Ideas for new enemies.

I would love to see some kind of zombie army in hell, that got in their ranks different dead soldiers from different eras of human history. Some one with rugs from modern clothes and helmets, some one with WWII and some one with more ancient and medieval gear, few pieces of armor and white weapon - broken swords, shields, axes, broken old rifles that act now like a clubs. They should be faster and more agile than normal zombie due to their military past. Some ones from modern era could act like suicide rush if You damage them enough. Some could toss at player anything that's in their way. Some could puke on player like Q4 zombies.

It would be interesting for me, but might be bit controversial for You, to have normal human soldiers as enemies. That's seeks cover, throw grenades, try to flank, do combat rolls and other stuff. There could be moment in game story when other big corporation try to storm UAC facility and steal teleportation technology. They sends their own private mercs aided with humanoid androids that operate in small groups. While most of game should be dedicated to fight against demons they could have 2-3 levels after player return from hell. They try to turn on teleport again and as a result they brings demons back and demons overtake them, so player must turn on some kind of destruction device in base and use their space ships to escape to Earth.

Also I would love to see different war machinery overtaken by evil tentacles and parasites, different size mechs, construction machines or security drones.