Basic settings: 6-10 players start up on the same team. The maps will be in the format with large mazes, such as abandoned mineshaft systems, abandoned science facilities etc. The goal is to reach the exit of the map. However, players will encounter AI-controlled "Odd Engies", like in the video. There will be checkpoints scattered along the map, and all dead players can only respawn at a checkpoint when said checkpoint is reached by a player. Players cannot respawn otherwise.
Enemies: Basic goons consist of small waves of Odd Engies. Only 6-10 will be spawned at any given time depending on player number. These engies can run on spy AI, basically being sneaky, ambushing, approaching from odd angles etc. They will also have different abilities, like cloaking, damage buffs, burn or bleed inflicting, agility etc. However they can only melee. There will be a few large "abomination" bosses in arena-esque areas scattered around the map, that players must kill to proceed. These can run on giant robot AIs, and will have large health pools and multiple unique special abilities, like fire spit (flares), toxic auras etc. There will also be rudimentary traps such as pitfalls and darts, things that would resemble what neanderthals would put down to hunt prey.
Visuals: The main point of the Odd Engies mod would be to be creepy as hell, and the visuals will reflect that. The maps would look like crosses between Ravenholm and alien hives, with corpse pieces, blood stains, glowing alien goo, pods, crazy lightings etc., with added surrealness like the corridor of arms in the vid for added creepiness. The engies themselves, aside from distorted models, will also move weird, particularly the abominations, which would move as if it's completely made from rubber in slow motion. There would also be scripted ambushes, for example a part where players must climb through a narrow pipe to proceed, and half-way through, the thing at 2:30 in the vid appears on the other side and players have to kill it as it crawls in after them.
Perks: To help with survival, players will get a few extra perks at the start of each round, similar to upgrades in MvM, though not requiring money and is in turn only allowed to choose 3 different perks.
This is very much just a concept that i came up with off the top of my head that i wanted to share. It'd be great if someone made this idea a reality though :)