I think it would be a great Idea to Implent a Fog of war system.
Basicaly, all the objects that are behind the wall will be invisible, since they dont make contant with the eyes of your character. Same for objects that are behind you, since you dont look at them, they will be invisible.
I'd like to see it as an Engine mark for level editor (Also should be available for Multiplayer) and as a difficulty choice in singleplayer campaign levels.
I'd like to see that feature, I think it will give Plazma Burst 2.5 a new dynamic and new challenges, this could possibly help to stop making certain singleplayer levels "Too easy" since you can see enemies through the walls and possibly shoot them through thin walls, which eliminates the challenge.
The AI is already too dumb in the game currently, all they have is that they have lots of HP's, powerfull weapons, and sometimes appear in great numbers. Find a wall, and then shoot them through the wall, since the AI is too dumb, you will manage to demolish them all... Boring as hell.
I want to see the AI being smart aswell, using tactics (Flanking, etc.), knowning to use weapons streight (Shotgun for close quarters, sniper for long range, etc.), and return fire at you even if you shoot them through thin walls (With weapons desinged to have high penetration values)?