I'd probably just give the mafia a power role, probably ungated, but I suppose something like a 1x ninja or a 1x roleblocker would work just as well.
Basically, either the town needs a little less or the mafia need
something
, but I honestly don't think you can really gate these town PRs without ruining the setup which is why I favor the "buff the scum" approach. They don't need all that much, but they do need something.