I agree with mr grimdawn. WE. WAN'T. CUSTOM QUESTS. (I posted this as an entire new comment just because i was worried you wouldn't read it because you ha'd to scroll down more on the comments you already read)
I've been thinking about a quest creator for a while, but I haven't come up with an easy way to let players create their own. I may just start with basic objectives (kill # enemies, collect # coins, reach x location, etc), and then see where we can go from there.
Guess you could just do that.
I believe an interface would be good. I'm imagining stuff like on the left side of your screen there would be something popping up with multiple tabs. Like defensive offensive and peaceful. Offensive would have stuff inside of it like kill 7 bla bla's and capture bla bla bla bla (With a capturable enemy flag that they could defend perhaps) Defensive would have stuff like defend your own flag or patrol this area for this amount of time. (You would have to stay in that area for a while and there could be scripted events happening like maybe an enemy coming from the side) Peaceful would be stuff like pick up jerry's bow and give it to him. Find the wizard. Or try to find the enemies flag. You could also do something like go to every spot in this area.