I think it would have to be nerfed to use McWoD. I'd want that system, if only because it's got a lot of potential (I like design work, so I'd house rule a bunch, but it's still pretty solid).
I mean, create a different setting and ideas behind the different classes. And there would need to be a Slayer class that's on par with the supernaturals, in terms of combat elements like DR and fast healing (or at least recovery during rest). Vampires would need to be different than in Buffy, though, in terms of the powers. Much higher budget SFX for one thing. And you'd need some kind of minion vampire stat block for the ones you make "poof".
Man I'd like to play this sort of game.