This would work in APC or a tank, not really in helicopter, as they are soft skinned, and armor if available (to heavy for Osprey) have many weak spots, and hiding gunner away from the weapon is not cover, but merely a concealment - he will get hit if someone spray the machine with RPK anyway. If we're talking about "good shots".. they will not choose a gunner, but a pilot instead, as they can take the whole thing down with one shot - and cause a lot of damage and confusion. It all have been discussed over and over again.
IIRC arctic ops are conducted with the gun ports covered until they need to be used, on all of the aircrafts, I guess gunners can handle that much, especially with a shot of adrenaline, as this is the most critical point of their mission.
The fact is - Osprey was not designed as a gun platform, and its direct defense capabilities are very poor, and that single, remote turret don't solve that problem.
Osprey as it is today, maybe is a nice machine to fly, but definitely it is not suited for a fight.
BTW - the problem of accidental shooting at own plane by gunners was already dealt with during World War II... 70 years ago.