Two behaviours I'd like to suggest while prone.
1. Your upper body can only swivel 90 deg (45 deg left/right) from your lower body angle with mouselook. Your lower body doesn't move at all. This seems more realistic and works well, e.g. on ladders and mounted HMGs.
2. Moving forward will auto-center your lower body (speed subject to test), while moving backwards will auto-center your upper body and first-person view. In effect, if you wanted to check your six, you would use a combination of #1 and #2. This works quite similarly to vecicles and three-point-turns.
Vanilla prone is so unrealistic when you actually spin around your hips. To make matters worse, when you're beside cover, this "spinning" has a higher chance of clipping the cover and exposing your legs (through the wall, etc.).
While proning is a defensively superior position, this will further make up for lack of mobility. Crouching will then have more use than before.
Something like that.




