with the recent patch and hotfixes, we've seen prone crawling go from 0 sight to 1 sight (and a bit higher secretly there for a moment). My suggestion is to split prone into two categories; moving and not moving. moving while prone will still give 1 sight, but not moving will put you at 0... as if you're feigning dead. while in this state, you can only alt look to remain at 0 sight. if you spin to look around, you'll jump back up to 1 sight. this could add some tense moments in the game when you're still and waiting for zeds to walk by, possible inches from you, all the while you're hoping you don't bump the mouse and move accidentally, aggro'ing the one next to you and possibly more.