Bioshock getting the MMO treatment?

A lot of sites are talking about Bioshock maybe becoming a M.M.O. I'm not sure how I feel about this. The game overall I think works very well as a single player but I'm not sure if or how they would do a class system? Since everyone can be a mage and a tank and non magical ranged dps, how do you create and limit the current abilities available to the player already?
Unless of course you get rid of the traditional class system, this could be very interesting to see if people by nature will find ways to create their own class. My hope is that with a open class system people will not so pigeon holed like in other mmo's.

I think one of the biggest challenges will be is how to keep the game feeling like you are closed in but having a large area to explore. One thing I think that could be done to keep the area from being overrun with players is to have the game instanced, or another thing that could be done is to have pre-requirements to entering certain zones. This could be done with keys, trinkets or randomly generated codes that you would have to enter into locks.

Another task to tackle are the endgame items. Traditionally this is done with gear, rings or weapons. Yet I don't know if any of these items would be that interesting to the player. The first thought is unlocking more of the story to learn more about the world and have zones unlock with a phrase that you hear or read in a text log.

But knowing this is just a rant from a random guy online, I am confident that whatever they end up doing, will be worthy of fifteen bucks a month.