I play it all the time, but the version i play comes with a policeman and a medic:
In the night turn, after the killers kill someone, the medic choses to save someone, if the selected by the medic is the one the killers choose then he's saved (the moderator checks all of this). After that, the policeman asks the moderator who are the criminals (they can only ask for one player per night) and the moderator tells the policeman if the player he asked for is a killer or not.
We usually play with cards but here we would have to use PMs for the night turns.
Having a policeman and a medic makes it more difficult to the killers but at the same time it's more fun. Plus the killers may pretend to be the police so they can blame a inoccent or even the real police or the medic.
I'm would absolutely play, and a GB theme mafia would be fun:
killers = akabane, a miroku maybe.
police = ban or ginji
medic =
(akabane IS a medic but i find it hard to inmagine him saving people instead of killing them) Paul could be a medic, for some reason i see that happening.