The idea of non-xp reward sounds good.
Maby a barber shop who takes a special coins. Or an imp who rebuild for a coin a room in the Home stead for you. Also the respect reward sounds good for competitionist. Those players (myself included) wants to min max too. So a reward from side quests who allows do it has the value. The demon for free respect (no money and all skill books returned) who accept the special side quest coins again ?