Only played the beta until level 5 but I couldn't help but think just re-using the format for a zombie survival shooter. Start the game up creating your Guardi-I mean "Survivor" with different skills, gender, whatever (and then being able to make more.) Have a storyline going that's there, but not too intrusive and allows you to free-roam areas. Leveling system, skills, loot. Even the armor system would translate well to clothing and other customization. Story-missions and side-quests and random stuff galore. Zombies would essentially spawn and "patrol" a dense, detailed, and large city environment and you can meet other Survivors as you play. Public Events would ensue in the form of a large L4D crescendo event. There would even be a hub somewhere called The Colony or something, which would act like the Tower. There could be PvP(vE) stages and Survival scenarios. I don't know, instead of MMO for a zombie game, a shared-world shooter would be best. Thoughts?