What about a simple global fog of war ?
What your character can't see is under a gray or black smoke.
If it is a black smoke, you see absolutly nothing, just a black screen.
If it is a gray smoke (or other system) you only see the default map. No way for you to know if there are dead bodies, loot on the ground, opened doors, opened containers, nothing that can lead to guess any player/npc activities in places you can't see. You have to check for yourself.
You might also be able to see 10% of the perception range of your allies, as you can see them too, through your squad features.
It would solve some "no roof" problems, and the "open doors" abuse too. There is no reason you should be able to see a door being opened 50 miles away.