AI gunner is a useless class.
Why would a human choose to be a gunner?
Ammo types.
What ammo types does an AI use?
None. (they even run around unloading guns with special ammo and switching them back to vanilla)
There is literally no reason to have an AI gunner. AI engineers are just as capable as AI gunners of shooting. Having AI is already pretty crappy compared to a human crew, and an AI gunner is just more of a handicap since there is literally no benefit at all over an AI engineer.
If for some reason you choose to be an engineer captain (I've seen it work well on galleons sometimes) and you have more than one AI on your crew, you get stuck with TWO AI gunners, thus crippling you even further.
Since you can't choose the class of your AI and AI gunners are 100% useless, I propose making all AI into engineers, or make a single class that's just generic "AI class" (gungineer) that both shoots and repairs.