This might be a feature already for all I know, but here we go:
I suggest introducing unique items and/or events that is one of a kind and not reproducable within a worlds life time. You might as what the point of this would be and point out that this games content is player driven (which it is not entirely).
One example could be to give a player bonuses to abilities. That in it self is not very extragavant or even unusual and is kind of achieved through quests (gildings given as rewards). A more interesting feature would be the boon of being able to produce items of higher quality than everyone else. For instance a smith could be given the ability to give his/her swords an extra bonus that nobody else in the world could give giving him/her an edge in the market. A clothmaker could produce superior cloth or hats or whatever. Can this system be abused? Not really since it would be limited to one character. I guess someone could bot, but it would have a limited impact. If the feats are given randomly and very rarely botting would give a small, but maybe not very big advantage.
How would these perks be distributed? It could be through the horid quest system. It could be given through doing credos? It also could be given randomly (once per world to one character) while doing relevant actions: smith smithing, clothier ..clothing, farmer farming etc...