Freeing slaves is an interesting one!
I guess my general assumption would be, when you restore a slave's freedom they'll be out the door before you can change your mind.
The dialog you get when you free a slave with undying loyalty strongly suggests they'd like to stay. I once tried this out with Aria after basically turning her into my warrior waifu. (Actually marrying her seems to make it impossible to still have her provide the quartermistress benefits.)
She seemed heartbroken and unwilling to go. I'd like it if I could free her and let her remain of her own will. For that matter I'd also love it if I could marry her and still have her join me on combat missions while providing me with quartermistress boosts.
Regardless, awesome game.