I'm also not so sure on the historical legitimacy of tank turrets shooting down aircraft...
The point is, if something is physically possible to be achieved within the physics of the ww2 combat universe then there is no reason it should not be available to be used UNLESS it hinders gameplay or fun for others. I have seen no evidence that this would cause anything but additional fun for those that wanted to use it, fun for those that get to attack the entire refueling operation, and an additional way for players to build teamwork and friendships <3.