Hmm nah, i think the whole thing about finding a tavern to sell slaves is quite good and besides, you dont get much money out of slave traders anyway.

There's alwasy Ramun the Slaver in Tihr's tavern who'll buy slaves as well.

Capturing high level slaves can actually net you a good profit. Like if you build an army of all manhunters (or just give your companions only blunt weapons) you can make alot of money selling prisoners.