The Sherman however has a rotating cupola. This is the reason you see photos of the .50cal on a Sherman in many different positions. The commanders hatch was mounted on a ball bearing race so the gun position could be changed easily by unlocking the cupola and turning it to a new position. This was a little different than the AA mounting rings on the M7 "Priest" self propelled 105 howitzer and on 6x6 2.5 ton trucks. Those rings were well designed to swing freely to engage aircraft with the .50 cal.
One issue with the current Panther AAMG is the number of different actions you need to perform in order to traverse the MG. These include moving the pintle position on the rail (key 5), resetting the magnification (key whatever), and traversing the gun at the new position (key 3), repeated as the target traverses the sky. I mention this in my bugfix thread (which is still in progress).
Anyway, you could make quite a number of game actions unplayable by introducing too many separate actions, each performed with different keys. For example, you could make Sherman players manually traverse the cupola (key 5) and then traverse the MG over 60 degrees (key 3), as in the Panther. Also, with more relevance to the majority of players, think of all the ridiculous complications you could introduce into the aircraft, thus making them less usable and the game less playable.
Thus, given that we have simplified numerous real-world actions in AH in order to make the game playable, this principle should be extended to the Panthers AAMG. Modifying all the other tank’s AAMGs to incorporate the same complexity would be a backwards step for AH, and would have play balance issues. Attacking GVs with aircraft is already way too easy – kind of like spawn camping, but worse.