This may be a big one, but in dissidia duodecim, Players were able to create own sidestories inside the game. For a MMORPG it would be way to huge I guess, but I would love if people could particpate in patchwise contests to create own questlines for the community. Those Quests could be adjusted by the developer team,making them fit into the lore of Eorzea. Is there any possibility that players get involded more in such creative stuff?

That would also encourage players to explore the game more, finding good placements for the needed NPCs, which NPC exist and are involved etc.