If you free the slaves, maybe simply allow them to stay with you, as they probably have no -safe- place to go to. Then allow a possible relationship to develop, if that is what both parties can agree with; more consensual. With the male freed slave it can still some sort of a dom/sub relationship -if memory serves me- but more like roleplaying in the bedroom. I don't know how much work that would involve, but it may require setting up alternate dialog while still using the lewd scenes that are already there. Or maybe, my approach is too simplistic?
Viewing post in Next Time, On Mdqp's Adventures... comments
I feel like it would be hard to make sense of going from them being slaves to roleplaying as such. Then again, it's tough to come up with some content that doesn't require a lot of work. Maybe I should just offer the option at the very start, and have them reward players with a "gift" of some sorts somewhere down the line.
You could do that!
Or, it might be corny/cliche, but you could always have them turn down being freed? Some kind of nice reply or minor reward for karmic goodness, but build something in that explains they can't be freed for whatever reason. Maybe their status as property protects them from past owners/debts/random vicious killers/whatever, or they'd just be enslaved again upon going off on their own, etc. That way you're 'thanking' the player for the effort but not removing the character arcs.
If you want to give an out to their arcs, I'd make it something crystal clear that you're skipping out on everything, won't be able to re-buy them or any other slaves, before the decision is made.
They do have reasons to be slaves, so I have been considering this alternative too, where they only accept being freed after they have become comfortable with the protagonist (as it happens for both characters, if you are on the "right" path with them). Acknowledging it is important, since freeing them is one of those options which make sense. Even in the game's world, slavery is a rare thing, with specific laws and rules (when done legally), so it would be weird to not give the option, even if it's symbolic with no actual gameplay changes.