If it reduced recoil more than the crouch it could be useful, but in general that would only be good for crawlers since the upward trajectory of your bullets would not hit targets behind your primary target. That's why I stand up as commando unless I'm shooting crawlers or spraying. Putting as many headshot-level bullets downrange as possible is the Commando's M.O.
It would also take a while to transition to prone stance, so tactically it wouldn't make sense to keep switching stances back and forth, and I doubt many players would want to be prone ALL the time. Crouch is easy enough to switch back and forth, it's simple, quick and effective. No need for prone, plus you'd have a large body on the ground presenting a larger area to block your teammate's movement.