I'd recommend increasing the EXP rewards for monsters in later areas. As it currently stands, it's more efficient to farm earlier monsters than it is to actually advance through the game.
I do really appreciate the lockpick sales, though; lockpicks were a consistent issue unless you went into captivity just to get a pile all at once, which was. Uh. A Choice.
EDIT: Oh, I'd also like to contrast with an angry comment I saw once by saying that the (human, at least) captivity section was some of the most fun I had with this game. I'll acknowledge that it's not for everyone, though.