Unless I missunderstood Pyro's dev update, it sounded like ME was going to be changed to allow CM's to setup missions for special events.  I suspect that it will remain in a beta state until those changes are made.  Pyro also mentioned wanting to bring back the old 8 player H2H.  If this is the case people hosting the h2h arena might be allowed to host missions as well.  I guess we'll have to wait and see, hopfully within the next year they'll have something..