First of all: I haven't read the whole thread, so I dont know, if someone had my idea before
How about a small world for all players, given by Nadeo, like a big city + some surroundings. In this world, there will be different "connections" like teleports or something that way. Using this teleport leads you to a online map-change platform where you can choose quests, you want to play.
This would fit in the Maniplanet-Concept, and could allow typical RPG elements like leveling your character with points and items.
The only problem could be, that everyone could create very easy quests with extreme high rewards. So there could be fun quests without limitations, which dont count on your character and real quests, which rewards you have to choose by a list, given by Nadeo.
Unfortunately there would be the same problem, but not that hard.
actually, you cant create a real mmorpg, if the player is able to create it, cause there will be cheaters. And creating a normal RPG (not mmorpg) would be too complex for the player to create.
So maybe there is this system like mentioned by me, but without evolving characters, or it is a game like wow + the possibility to create your own fun quests...we'll see