I'd think it would be pretty neat if we could manually assign colonists to escort prisoners around, it could come in useful in terms of taking them to different places, different prisoner cells maybe, or just simply releasing them back where they came from, however I was thinking more along the lines of taking them to an execution area where they could be dispatched (in front of an incoming wave of raiders maybe?) or they could transported to an arena of sorts where they would fight it out with other prisoners or colonists in exchange for freedom.
Edit - With the arena thing, it might be an option for colonists to watch these gladiatorial fights take place, boosting their mood for a while dependent on their personality (pacifists may hate to watch such a brutal event) Could tie in with the factions being introduced in alpha 3, the more feral and predatory factions may favour you for doing so.
I'm getting off topic now...
Edit - With the arena thing, it might be an option for colonists to watch these gladiatorial fights take place, boosting their mood for a while dependent on their personality (pacifists may hate to watch such a brutal event) Could tie in with the factions being introduced in alpha 3, the more feral and predatory factions may favour you for doing so.
I'm getting off topic now...