More side quests or be allowed to redo the side quests we have already done. Add more leve quests.
Make it viable to level from killing world mobs by increasing the exp per mob and chain time limit so you can chain far more mobs than you can do now.
Make it viable to add user made quests by adding some kind of quest editor that enables someone to make up quests for other people to do, decide how much exp they get what rewards they get from a selection SE seem applicable for each level. They could choose what NPCs you need to talk to and the dialogue that is said etc.
You could pick up these quests from the Leve quest chap under a tab called user quests.