A cool concept but hard to make would be sports, and much like orginizations, you could have teams and leagues that fit into the story. It would be quite hard though, first you ahve to think of a cool inovatave sport (nobody wants to play soccer on AO)a good example of this would be final fantasy 10's blitz ball, it would also be hard to figure out how it works because you have many thing to wory about such as lag, FPS, and variouse other user options...but still I think its a cool idea