I believe the player should hold some level of control over sentries. It can spark war between players if a sentry opens fire on another's subs, so I think it would be beneficial to have a control screen for them. I think there should be control over whether they fire on subs not headed for a station owned by their owner or allies' subs.

Let me swing the question around; If your sentry is firing on someone you don’t want it to be firing on, then why is your sentry so close to them?

the entire game is built upon predictability. if a player can at any moment change which sub the sentry is firing on, it creates unpredictable situations, which then reward those who check the game obsessively, and we don't want that.

the only specialist that breaks this predictability is the navigator.

I think default should be always fire, with options for each player. E,g, fire always, fire if approaching territory, fire if approaching base, do not fire

Agreed. Or some control by alliance. It is not unlikely to be near an ally. Firing on them with no control is an unwanted outcome.

If my subs were fired on by an allies sentry I would demand restitution.

I think that happens in real life sometimes—countries accidentally firing on other countries aircraft.