This is something that has been brought up again and again and suggestions made and approved, but nothing really has changed.
In the Underdark when you are a prisoner, there are a lot of creative ways in what you can do with your prisoner:
Blood sports (let them fight for their freedom and your entertainment)
Torture
Enslavement
Experimentation
Curses
I'm sure there are a lot more options which I can't think of right now being on a lack of coffee and early morning brain.
But for the Surface (especially as a morally good guy/woman) there are really not all that many (and no real creative) options on what to do with a prisoner be they local criminals or UDers (at least not what I can think of):
Interrogate
Leave them sitting in your jail cell
"Put them in" a stockade and hope they go along with it and not just run off
Kill
Let go
Ideas from the past were things like a prisoner collar in which the prisoner could perform tasks like gathering resources, killing rats etc. to work for their release. Little quests so to speak to do community service and work off their sentence. These ideas were well received years ago, but never implemented.
So, without mechanical solutions to this problem (for now), I would actually be really keep to hear what sort of RP you think Surfacers and team "good" could apply to give a more enjoyable experience to baddies when/if they are captured.