[DustyPorViva]

Well the thing is with that type of server is it offers many things that MMO's thrive on.
Diversity: Players/humans/races can only get so diverse from looking like the next person. Monsters on the otherhand can just about look nothing like the next, while still having maybe a 100+ designs.
Leveling: Instead of being stuck leveling one player, of one race/class, you'd be able to choose and level up different monsters when you feel like it, and mess around with different skills.

And some other stuff I had thought about while posting and forgot. Either way, I'm sure people could think of a ton of things to do with that type of server. It's a wonder why Nintendo hasn't done one with that franchise, it seems like the obvious thing to do with it.

EDIT: Oh ya, and lots of people like collecting/trading and such. That'd be a plus as well. And instead of events giving away special weapons, you'd be able to have a chance to capture rare monsters and so on. Lots of possibilities.