I really hope each faction has a series of story missions. New Monarchy, FWC and Dead Orbit could all take place within the city districts, having you overthrow council members, or fighting for territory and equipment. It also gives us a good reason to actually go into the city. As for Osiris, I suspect a few missions on Mercury, perhaps some crucible related challenges. God knows for seven seraphs (Europa? Saturn?) You guys have any ideas for faction missions?