Just finished my Heroic playthrough of this and I gotta say this is my new favourite way to play Halo 4 along side Halo 4 Reflow! (Mythic Overhaul is still pending until Jaqui fixes the crashing issues lol)

Here's the things I really liked:
-replacing not only the Forward Unto Dawn's in-game model with the Halo 3 one BUT also changing all the holograms to match!
-giving us an actual proper showdown against the Didact
-Chief changing armour halfway through
-the best rendition of Promethean Soldiers I've seen yet
-giving the Knights their creepy human faces like in the concept art
-Promethean-Elite hybrids like seen in concept art
-an actually viable Halo 4 Plasma Pistol that doesn't run dry after 50 shots!
-the BEST design for the Storm Rifle I've seen
-giving the Elite on Composer a Gravity Hammer. I did not see that coming and was pleasantly surprised lol
-all the Promethean weapons. They feel SO much better to use now
-vehicle health bars (how is this not standard?)
-the Mantis' new Gauss Machine Gun. That thing RIPS
-seeing the Revenant in action

And here's some suggestions/criticisms:
-while you said you aimed to reduce the frustration in fighting Prometheans, I think the Knights could use a little more work on their teleport spam. They still teleport a bit too much
-what's happening with the Railgun? It works fine against everything EXCEPT Knights. I put four shots consecutively into a Knight and it didn't seem to have much effect. This is particularly baffling as I always saw the Railgun as a dedicated Knight (and Elite) killer in the vanilla campaign
-I can understand reasons as to why the Stasis Rifle isn't usable by the player and I appreciate that Watchers are capable of using it as a way of still incorporating it into the game, but I'd like to suggest the following: Stasis Grenades. I remember Mythic Jaqui mentioning that Halo 4 can support up to 8 different grenade types, so I think it wouldn't be too far fetched to take the Pulse Grenade, change its colour and give it a stasis field effect. Please let me know what you think, I think it could make a nifty utility

All in all, really enjoyed the mod! Added to my favourites!