A suggestion from Phil Lim of Vancouver:

Basically, the Bus Driver plays for the civilians and he "switches peoples' seats." He wakes up at night and points at two people. These two people (let's call them Person A and Person B) are now 'switched' for just that night. Anything that happens to one of the two people chosen (be it targetted by 'Mafia', checked out by the 'Angel', or sequestered by the 'Magistrate') actually happens to the other person. So, for example, if Person A gets targetted by the Vigilante, then Person B is the person that actually gets killed by the Vigilante. Interesting results often occur, for example, Mafia members may end up killing themselvesbecause their target was switched with one of them.