TL;DR: The prosecutor role is a mafia role whose vote counts for 2. Therefore, in most (if not all) situations, everyone can self and the prosecutor dies. Selfing should only count for one vote.
Okay, most of you who are reading this probably already read the TL;DR, but to reiterate, if everyone on the village side selfs, mafia will have to follow to avoid being caught out as mafia. The prosecutor's vote counts for two votes, so if they self, they die.
I noticed this issue when I was playing a setup of mine called Ode to Samantha: https://epicmafia.com/setup/1462597
Now, this was a fun setup I tested a good few times in unranked and it seemed relatively balanced. Shoopie agreed and upvoted. Mod upvotes count for +20, so this allowed it to be played in ranked. However, in its 4th ranked game I realized (thankfully before anyone else did) that if everyone selfed, prosecutor would die. Unless nilla refused to self, in which case they would probably just be shot and then everyone would self.
Immediately, I downvoted my setup to get it out of ranked and got Shoopie to remove her upvote. And this isn't applicable only to the Ode to Samantha setup. It applies to almost any setup. The only thing I can really think of that would counteract that is adding a judge, but if they die, village can still do this. It's an unfair autowin.
So, in order to make this a fun and usable role, the prosecutor's self-vote should only count for one vote. Why does this not apply for judge? Well, potentially that would be a good cover-all too. But it would be rare for judge selfing to be a problem (maybe in traitor setups). Judge would not self for mafia, and village would not use this tactic to try to kill their own judge.
So, I'd like to hear your input, but personally I think something needs to be done about this. The role's effectively useless otherwise and this will allow for more potential setups that we haven't yet seen.