It sounds great on paper (uh, what?), but the comments here made my expectations drop from "It's gonna be SWEET!" to, "Cautious optimism".
I would love a GTA-like multi-player game where you could raid other gangs (player guilds), or banks (npc). RPG stats that increases with use and skill, not while grinding xp. Side missions that includes driving, racing, kidnapping, assassinations, etc. Gang leaders could have diplomacy with other gangs (non-agression, association, war, etc.). No "trade chat". You'll have to actually meet people to be able to talk to them, unless you already met them before and have them on your friend list. A game like that would have tremendous potential. In fact, I think I'm gonna start designing one right now!