Theres always something that can be done. The problem isn't as much that you can park inside, and shoot someone to steal the kill, but that it renders them completely useless Because your model blocks their sights completely, and even if you do turn tour turret around and shoot them, the shell doesn't gain any lethality until the end of the barrel. Now Since there is nothing to do, why not make the shell originate from the center of the turret making it easy enough to kill them.
I turned my turret directly through the Flak and put a shot "into" him. and my shell flew off into the distance.