I kind of have a problem with weird vision-altering mechanics, since the algorithm right now is still pretty shaky. Still, I see the need for it in this context, since it's currently hard to play the sniper game in anything other than an empty room with pillars. Hallways would just be a nightmare. Unfortunately, I can't think of a solution other than giving the player the first move when an enemy moves into sight (or you move into its sight), and that seems pretty imbalanced. But it would give you a way to fire around corners without eating a heaping bowl of damage.