Thinking out loud really but this seems an eminently possible addition...maybe even content for the game *gasp*!
The Matrix influence is clear in Underworld, from environment to clothing style they share a heck of a lot. Re-watching Underworld and catching Blade 2 last night really made me think the perfect modern era mmo could be fashioned to that world and indeed how easy it would be to use MxO as a base in the process.
3 Organisation or maybe an elite class extension of other orgs 
Vampires
Werewolves
Monster Hunters
The city stands, many of the abilities stand....so much...and the near continuous conflict actually makes sense - yet as I stare out into MMO land carefully skirting round the massively overpopulated, overblown and overrated Fantasy Genre no one has done it yet.....Why not?...
Maybe it can't fuel a game in its own right but then maybe that is another area into which MxO can plunder, lets have the Merovs split into Vamps and Werewolves, infected rsi's which have a new meaning and purpose in the game with a few custom abilities for these classes the draw would increase away from zion and assist in the population balance etc. In the wake of the monster genre films the game also garners a new aspect to advertise.......