Once a mafia dies, they should tell the medium to whisper to the other mafia to co-ordinate... which can leak of course...
Because the graveyard messages are anonymous to the medium, the dead town can pretend to be the dead mafia, to disrupt the mafia who will try to say which the town PRs are. Not being part of the mafia meetings prevents codes from being used.
The medium won't realise that they are actually maf sided until someone dead starts talking... Dead town should stay quiet so as not to let them know until one of the mafia is killed. Could work well with Miller, Godfather, Insane/Rookie Cops etc.