A moderately expensive in-game item allowing you one redesign of a single character?
This would allow you to change their gender and appearance, but not their race. With characters taking as long to build up as they do, it's sometimes irritating to spot problems with your design later on - it's not like you can just reroll. It would also make a nice money sink.
Apologies if this has been suggested before. I did check, but if it has been suggested, it's become somewhat buried in the forums somewhere.