Keep em coming. I'll answer in detail later. One thing though: Your Python is very similar to what i plan on doing with the Boa.

My suggestions are a few:

First, have the Sectoid Captain and Commander retain the unique characteristics of the EW version, that is, being able to Mind Merge to strenghten their underlings. Captains would possess normal Mind Merge and Commanders Greater Mind Merge. There's a Sectoid Commander mod in the workshop already, so I reckon this custom ability isn't very complicated to implement.


Second, MECs need a few more variants. Just as we have the Auto Doc, we could have the Matrix, a MEC that supports his allies aggressively instead of defensively. Using their own version of Mark Target, which would increase Aim and Crit against the targeted enemy, combined with a wider, more damaging to the environment Micro Missile Volley, the MEC Matrix would serve as a commander of sorts, buffing all mechanical units around him at the expense of his armor. His AI would prefer to stay back just at the edge of conflicts.


My third and final suggestion would be to start integrating more mixed pods in the late game, growing in both size and strength. After a while, ADVENT stops giving a ♥♥♥♥ about keeping appearances and just starts fielding what's more effective.

A high-ranking Kommissar might find himself with Mutons at his disposal, with a gunslinger in toe. With their powerful plasma grenades, the Mutons can open the path for the Komissar and the Gunslinger to clean up poor XCOM stragglers with well aimed pistol shots.

Wardens could replace one Stun Lancer of his with a Berserker. The Stun Lancers would work to go around the enemy XCOM squad and flank them, while the Berserker runs straight into the fray, making herself a distraction for more tactics-minded squadmates to use. A particularly lucky/unlucky Warden could brag about having a Firestarter amongst his mix.

Adepts would gain some underlings, ADVENT Psi Operatives. With supporting skills like Stasis, Inspire and Insanity, the Operatives coordinate well with the Sectoids they serve with, making sure they can survive long enough for the Psi Zombies to start wreaking havoc.

Heavy Tactics Officers gain Suppression, and are paired with Sentinels and Strikers. By holding the terrain and keeping the traitorous XCOM pinned down, the Sentinels and their Officer give time for the Strikers to *ahem* strike deep onto the enemy's flanks. A powerful Tactician would love nothing to replace his strikers with ICEs.


Combos like this should start to appear, IMO, as XCOM's troops become complete. The late game should not be a complete curbstomp by our part, instead the ADVENT Administration should give everything it has to repel the rebel threat!

There's two units I've noticed without any variants so far, the turrets and Sectopod, is there mechanical limitation behind this, or just a lack of good concepts?

I've got a few ideas kicking around in my head:

Turrets:

-Interdictor/Interceptor/Oppressor or some other name referring to its function of limiting movement

A version of the turret focused on overwatch with some accompanying perk(s), Guardian/Killzone/Covering Fire/Suppression(AOE suppression?) that cannot or chooses not to fire normally. Its role is to allow for other units to take advantage of XCOM's inhibited movement.

- Beacon/Pyre something related to fire

A version of the turret that's armed with a flame thrower and sets areas of the map on fire to obstruct XCOM. Ability: Firewall, makes a line of fire perpendicular to the firing direction of the turret preferably in the middle of XCOM making it hard for them to move forward or retreat as one. Does not have to be a solid line of fire.

http://i.imgur.com/bjBM2uL.png

Mech:

- Mech Eruptor

A version of the Mech that fires an incendiary micro missile barrage with very large spread (like 8+ tiles) starting fires where they land. Low damage and unlikely to actually hit XCOM, but start substantial fires. Kind of like an instant Blazing Pinions that has low AOE and damge. Possibly upon reveal? Would fit in very well on terror missions, never enough enough mayhem :D

@DerkBK: ah, reading through older posts it seemed like your plans for the Boa were somewhat different, most notably making it a melee unit, possibly with stealth. If your plans for it are similar to my ideas, that's cool; great minds think alike. ;)

@Makko: a few others have asked about the Sectopod and DerBK said that he feels like the Sectopod was already in a good spot in the vanilla game, hence no need to tamper with it. Especially since they are quite rare.
One thing that might be worth considering, however, would be removing the 1-per-mission cap for Sectopods and Gatekeepers. At least for the Commander/Legend difficulties.

Here are my two cents:
-The advent sentinel should have covering fire along with ever vigilant to make them more threatening.
-The sectoid soldier's armor is a bit too much but they should have +2 hp in legend and +1 hp everywhere else.

Artillery: a turret or mec
They have an ability that marks a spot near them (could be shaped like the evaczone square) and bomb it next turn.

Alright, here we go with a first round of responses. I hope i covered everything!

-->Python: The role of a melee Viper is going to be filled by the Boa. There is some overlap between your ideas and mine, maybe i'll use something from yours if something of mine doesn't work out.

-->Stunlancer AI: I already made substantial changes to how Lancers behave. I think they already do a lot of the things you want to. The part where a certain number of Overwatchers should stop movement is something that i want to do, but as a global thing, not tied to Lancers.

-->Prime Negator Purge ability: The Negator already removes effects around him while he lives, so that effect wouldn't do much if it also triggered on death. An immunity could be interesting, but i don't think a narrow ability like that is worth the effort.

-->Sectoid Mind Merge: Good idea. I will take a look at the Sectoid Commander mod and see if i can whip up something similar.

-->MEC Matrix: I think a marking ability makes them overlap too much with the Captains, who i want to keep as default leaders for Advent pods. A variant of the Micro Missiles that has low damage, but high environmental destruction sounds interesting, though.

-->More varied pods: I am still thinking about how to go about this the best way. I do want to do something like that, but every solution i would come up with would conflict with IESS, a mod that is pretty much omnipresent at this point. I would have to integrate something similar into my mod before i can start defining pods better than now, because the vanilla spawn RNG is limited in a bunch of annoying ways. I will keep working on a solution for this problem as a little side project. Maybe i can offer an optional ini file at some point that can be used instead of IESS.

-->Kommissar with Mutons: Sounds like an idea. Or i could just make them team up with Demolitionists to keep the pods rooted in Advent units.
-->Wardens with Berserker: So... a game warden? Interesting. Yeah, i can see that happening.
-->Psi Operatives: I don't think it is very flavorful for Advent units to have psi abilities. I only made the Adept and even he is somewhat underpowered in the Psi department. It's by design and i plan to stick to it. The whole point of the Avatar project is how completing it makes the aliens invincible because they now have units with exceptional Psi powers. Giving those powers to some troopers doesn't work for me. So i am not a fan. If i were to make a heavy psi unit, it would be some sort of non-Advent alien like the Gatekeeper or a Prime Sectoid.
-->Heavy Tactics with Suppression: Suppression on units that aren't meant to have them are all kinds of buggy. I could try it, maybe it works because the HT Captain carries a cannon. But i am not optimistic.

-->No Turrets/Sectopods: I don't think new Sectopods are needed. They are scary enough. Turrets are something that i want to experiment with. Stuff like the Overwatch Turret is going to happen then. Also, gud jorb on the image. I can appreciate some random MSPaintery.

-->Mech Eruptor: There are already so many fire based enemies in my mod. The Wyvern pretty much does exactly that. I should mix it up and throw some gas clouds or acid pools around instead ;)

-->1-per-mission cap on Sectopods and Gatekeepers: That's a thing? Huh. I think it's somewhat healthy to have it, to be honest. Even if it's just in the name of variety. Now that i think about it, i am actually thinking if i want to restrict something else to 1 per mission. Chryssalid leaders, for example.

-->Sentinel with Covering Fire: There are a few passive abilities in the game that straight up don't work on non-Soldiers. Shredder is an example, it has to be replicated by modifying the weapon instead. I tried giving the Sentinels Covering Fire earlier today and it seems that ability also doesn't work on non-Soldiers. More testing may be required, but at first glance it's not looking good.

-->Sectoid armor: I will remove the armor from the Soldier and give it to the Captain with the next version.

-->Artillery: That sounds like a sweet turret to me. Insane range and squad sight should be part of the package, of course.

@DerBK How about guardian? You can put it for elite or advanced sentinels only. I'm glad you liked the artillery idea. Played some valkyria chronicles and got the idea for that when I saw the mortars in the game.

Sentinels already have Guardian.

@DerBK:

-making that AI tweak with regards to Overwatch global rather than unique to Lancers is even better. Good call.

-about the Prime Negator's Purge ability: I think this issue could be dealt with by expanding its radius. Solace works in a 4-tile radius; how about making Purge affect all allies in a, say, 8 or 10-tile radius?
There isn't much out there that can counter Psi Operatives so I think this would make a nice addition.

And now some other ideas:

1) New enemies:

• Viper Leaper: these Vipers can use their tongue as a grappling hook, allowing them to rapidly move around the battlefield. They will use this ability aggressively, taking full advantage of elevation bonuses and relocating to elevated positions from which they can fire accurate and, possibly, flanking shots.
They don't have the Poison Spit ability and, obviously, can't use the Bind And Crush ability.


• Faceless Mauler: a mid-late game variant of the Faceless. In addition to standard things, like having more health, defence, dealing more damage, being able to shred armor with their attacks and regenerating their health at a higher rate than regular Faceless, they also possess the following abilities:

-Flurry: performs three attacks against a single target in quick succession. The attacks come with a -15% chance to hit and cannot critically hit. 2-turn cooldown.

-Death Clutch (passive): grants an automatic attack against any enemy who moves within or enters the Mauler's melee range. This attack cannot crit but deals substantial environmental damage. Once per turn.


• Tempest: in essence, a Prime version of the MEC. Other than being tougher, more accurate and more resistant to hacking than other MECs, Tempests also have some unique characteristics:

-Active Protection System (passive ability): the Tempest is fitted with a system that is able to deflect incoming projectiles, causing the first shot fired at it to miss*. Once per turn.

-Firefinder Sensor (passive): the Tempest boasts an advanced sensor suite that detects and tracks incoming fire to determine the point of origin, after which the Tempest immediately returns fire at the source. Works on targets out of the Tempest's line of sight.
This shot cannot crit. Once per turn.

-Reactive Armor (passive): the Tempest's core components are protected by additional layers of armor, making it 25% less likely to be critically hit.

Tempests don't have the Micro-Missiles ability and can't use Suppression. They are also slower than other MECs.

These are all passive abilities but I think this combination makes for an interesting enemy who requires a different approach. Their Firefinder Sensor also makes them a threat to any complacent commander's Sharpshooters.

*possible conflict with guaranteed-to-hit abilities?


2) Changes to existing enemies:

•ADVENT Warden: the Warden's stun baton is now guaranteed to stun the target if the attack hits.

• ADVENT Sniper and Guardian: the advanced and elite variants of these are now equipped with a grappling hook which they will use defensively, trying to stay back and provide cover to their allies from afar.
EDIT: since a solution has apparently been found to make Covering Fire work for ADVENT, I'd give it to these guys, as I originally planned.

• ADVENT Striker, Breacher and Assault Stun Lancer: the advanced and elite variants of these now have the Deep Cover ability.


3) Enemy squad composition:

• Pyro and Infector Mutons are more likely to spawn with Demolitionists and Wreckers to make up for their lack of grenades.

• Regular Mutons are more likely to spawn with Strikers, Breachers and Assaults, as they can best take advantage of the Muton's grenades/Suppression.

I do have another suggestion, one that I was cooking up, a personal mod of sorts, but I don't have a lot of time in the next couple months. I don't mind giving you full liberties with my idea if you like it.

I noticed in the late game ADVENT, both the Administration and its alien allies/subordinates, don't really have an expy for XCOM operatives. With which I mean there's really nothing which can stand up to your squad, contrary to the early game, where engaging a pod of even troopers without much thought could cost you the mission in Legendary.
To fix that, I propose - The Lambda Squad.

The best of the best, the elite of ADVENT. The Lambda Squad is the Administration's response to continuous reports of elite resistance elements steamrolling through the peacekeeping forces.
Their stats were thought with the mid game in mind, where I envisioned they'd start appearing, but can easily be adapted to the late game if needs be, maybe by introducing elite versions.

Units:
-> Lambda Operative:

Perks - Deep Cover, Ever Vigilant, Covering Fire and Tactical Advantage (custom perk: Essentially Implacable in an AoE. Killing an enemy unit gives all allies in a small radius a free move-only action).
Good Aim, 13 mobility, no armor and dodge, 8-10 health.

Each squad (read: pod) has two or three operatives, the third sometimes replaced by a technician or a breacher. The Operatives are the pinnacle of ADVENT's troops, and it shows. The Operatives gain terrain and don't let go easily, punishing carefree movement of enemy soldiers. They immediately cease the opportunity of a downed foe, moving into a position that solidifies their advantage. Failure to respect their strengths will lead to a snowball of death.

Essentially Troopers on 'roids that will ♥♥♥♥ your day up if you make one mistake. A Lambda Squad is meant to be a mini boss fight, and as such they pretty much require an ability to be used to break their overwatch, or explosives to destroy their cover.


-> Lambda Technician:

Perks: Aid Protocol, Medical Protocol, Sabotage (custom ability: Psionic Bomb without the explosion that comes after, costs 1 action), Energy Shield on a 4 second cooldown.
Average/Mediocre Aim, 6-8 health, 2 armor, 11 mobility.

The Technician is what happens when the Elders start knicking ideas from XCOM. Using their own drones (I was in the process of exporting the drone model from EU/EW, but my PC died. Could try doing it for you once I get it back). Their job in the field is simple: provide tactical support to Lambda forces by keeping them alive or forcing their enemies to waste valuable turns reloading, either keeping them grounded or unable to fire for a turn. Their renewable Energy Shield means they're never to be ignored, and are to be taken out immediately.


->Lambda Breacher:

Perks: Blast Padding, Untouchable, Deadeye (can only be used with a flanked unit)
Mediocre Aim (can only reliably hit flanked and/or close shots), average mobility, no dodge, 1 armor and 9-11 health.

The Breacher is a continuation of Lambda's snowball nature. If XCOM operatives are smart and give him no openings he'll be of little use, but a single mistake can be the difference between life or death of a squad, as the Breacher will almost certainly kill at least one operative if caught in a bad position and Blast Padding and Untouchable will make him a pain in the ass to kill. The Breacher offers some advantages and disadvantages over a regular Operative, but must be dealt with in a much different manner.

-> Lambda Leader:
WIP, I was thinking of a Kommissar on steroids sort of deal, with an ability that fires a pistol shot that if it hits marks the target for +15 Aim.


As for looks, I was thinking retextured Stun Lancer (Orange and White was on my mind) with a cape, and retextured Shieldbearer, Trooper and Officer for the Technician, Breacher and Leader, respectively.

They'd never appear in normal and retaliation missions unless in certain conditions, but they'd always be present in facility missions, and would have a chance of appearing in UFO and Guerrilla Missions as on-the-site reinforcements (which means, they arrived before you did). A Dark Event would make their presence as regular reinforcements a 50% chance on all missions, except they'd arrive immediately once the red dot was lit (much like the reinforcements in the Haven Defense mod).

The objective would be to give a sort of early miniboss in the form of a squad of powerful enemies designed to work together, much like your own forces. Like the Avatar and the Codex before it, a Lambda Squad appearence would pretty much force you to use some limited use abilites or consumables even in a standard engagement, if you expect to leave without casualites.
Initially a Squad would be composed of a Leader and two Operatives, as to not make it completely impossible to engage in the mid game if triggered with other pods active. As the game progresses, this turns into a 4 then 5 man team, with either a Breacher or a Technician guaranteed to appear as the late game draws near.

In my latest campaign I encountered a huge amount of heavy mechs, got very boring fighting them. Perhaps that was just the luck of the draw, but if not more variety would go a long way. Did not see any wyverns and maybe 2 firestarters by the time Sectopods were showing up.

The covering fire must have some kind of flag to make it XCOM only right? Can't you somehow remove it? Since they overwatch most of the time, how about deep cover?

@Hansworth:
This reddit thread has an explanation by a dev (fxsjosh) on what i suspect is also happening here:
https://www.reddit.com/r/xcom2mods/comments/4corhc/add_holotargeting_and_shredder_to_weapon/

Basically, i am waiting for that fix. Hey, maybe we are lucky and it's part of tomorrows DLC, right?

@Makko:
May be luck of the draw, may be bad spawnweighting on my part. Getting that stuff right will be an ongoing process that requires lots of feedback. That you didn't see any Wyverns or Firestarters is strange, however. I see Wyverns all the time in my campaign (almost too often) and Firestarters appear decently often as well for me.
When you say you encounter a lot of heavy MECs you mean vanilla MECs? Or AutoDocs?

Huh.
http://steamcommunity.com/sharedfiles/filedetails/?id=657339391
I will look into that.

EDIT: Okay, that works. I can integrate that fix into my mod and Covering Fire does what it's supposed to now.
One small issue: It doesn't say Covering Fire on the FlyOver text, only the regular "Overwatch". That could set someone up for a nasty surprise...

Of course it's bg, he fixes everything in this game. Glad covering fire works, sentinels are now very threatening. The covering fire text bug is rough but people should learn from it afterwards. Also now that covering fire works, are you planning to remove ever vigilant?