Since the search tool seems to fail to turn up any hits for this, I was wondering what the current developer stance is on User-created content. I believe 河豚 or Tanaka was talking about it before he got hit by Vanish/X-Zone, but I may just have been imagining it.
People seem to have very-strong-opinions on how the game should be balanced and run, and people also have very-strong-opinions on the current issue of game content. Implementing a strong user-generated content facility might take rather a bit of work, but could ultimately go a long way towards alleviating both issues. It also allows people to exercise their creative muscle, and self-expression is quite an important aspect of any engaging social medium. I believe it is also an incredibly engaging factor that has been largely absent from online games since the predecessor of modern MMORPGs, Ultima Online.
On the feasibility aspect, I would like to point out that Square-Enix has previously attempted things like this (the Moblin mazes in FFXI, and Dissidia 012's user-created quests, to wit). What's more, such a system actually does already exist in games such as City of Heroes or Star Trek Online. Naturally, moderation and farming abuse might be concerns, but I'm pretty sure both are addressable.