Will it be possible to have the manned turret controlled by an AI NPC and if so, how would it be penalized since manned turrets already lose one size compared to unmanned ones?

At this time, we intend no additional penalty for hiring NPCs to man your turrets, just the UEC cost of their friendship. Since there aren't options for trading manned turrets for unmanned turrets at the moment, this will probably handle the matter for the immediate future. The turret sizing rules, as with many things, undergo review and vetting over time to see if they comport with our solo-play/multi-crew game balance aims, so if it's clear to us that a course adjustment will get us closer to that goal, we reserve the freedom to run with it.