I admit, what you've presented as an idea sounds like the fictional 'Ishikaze' game which serves as the setting for Dan Hess' relatively light-hearted comic 'Realms of Ishikaze.' (Which just concluded after 7 years.)
As background, Ishikaze is a game where the developers created tools; the players can create additional content/quests/items within the game, but a lot of core mechanics (how combat works, how physics work, how leveling/resources work, what races are available as player character avatars) are set in the engine itself (so it's not completely 'build whatever you want' like Second Life is in the real world). Major quests, events and game additions are handled by administrators (actual employees of the company).
That's what the comic uses as its setting, and then tackles story arcs about things like hackers trying to gain advantages in-game, or boys who self-identify as girls and so play a female character in-game, or what happens when the developer loses legal control of his own creation and the new shareholders want to monetize it through in-game advertising (and how the players react), etc.
Anyway, from your revised post earlier in the thread, it sounds like you're sort of trying to build a real-world equivalent of Ishikaze. Which is great; people can get very invested (look at Second Life, after all). But also keep in mind that even if you have a diehard core of content-creators who are deeply invested in the game, what makes or breaks an MMO (which has upkeep costs, for servers and bandwidth and all) is the general playerbase. If it's a subscription game, will they keep paying a monthly subscription fee? If it's free-to-play, will they buy premium add-on items?
That bulk of the userbase is not necessarily the people who make content and get deeply invested, any more than the general userbase of LotRO are the people who write the various Lua client addons (like the Palantir plugin that I live by). The bulk of the income is the general players... and what you need is something to keep /them/ hooked and invested. You can get tons of people in during a beta or launch period easily, but the key is keeping them when the next launch hits.
Maybe DCUO has a ton of people playing it right now, but when Bioware goes open beta on The Old Republic, how many of the casual "I'll give this a try" DCUO players may jump ship over to go "I'll give this a try" on SW:TOR, instead? Even though the MMOs aren't even remotely the same setting? What makes or breaks an MMO is the ability to keep paying players (whether they pay through subscriptions for a pay-to-play game, or through premium add-ons on a free-to-play) after that initial "ooh, shiny!" period.
(Sorry for rambling. I used to be a game developer.)
