We should try to design a balanced open RMM.
I have at least one role suggestion.
There could be something like SmallTown. Or were you thinking something simpler?
Depends on how you define "simple".
I would have suggested a regular open paradigm, where the roles are distributed randomly but all possible roles are known from the outset, possibly with more possible roles than there are players. People can still fakeclaim, but they can't just wildly invent new fake roles.
As a group, we could propose new and interesting roles with mechanics that might not fit well into a regular game. Since it is open, it also means that everyone can voice concerns that a given role or combination of roles is overpowered or underpowered.
By the way, the role I have in mind is a Jailkeeper variant. Instead of selecting one player each night, the JK can jail X number of players. Jailed players cannot target non-jailed players, and vice versa. However, jailed players can target jailed players and non-jailed players can target non-jailed players.
X might be "half the town". Thematically, the JK should always be outside of the jail, which means mechanically the mafia needs to have a way out, lest all members be caught and locked every night. That would probably be in the form of X-shot keys, one player who is immune, or maybe certain powers that can slip through the bars.
Something else I'd like to include has been done a few times now, in various forms, I think. That would be the multi-cop -- choose X players to investigate, get results that are not entirely clear. Of course, it's too strong to have the result allow for "none of these are scum". Maybe "the majority are scum/town"? It depends on X too.