The 1-shot version of many a role would be a great addition. (A 1-shot cop being a cop that can only inspect someone once, a 1-shot doc being a doc that can only protect someone once, etc.) But, instead of adding all 1-shot roles separately, it'd make more sense to have a single 1-shot role modifier that can be applied to any role it can work with. The same goes for some other alternative versions of roles. I realise this is probably not the easiest thing to implement, but it'd make setup design much more flexible and it'd allow for the creation of quite a few classic Mafia setups.

Example modifiers:

Weak roles die if they target scum. Can be given to roles with a meeting that can choose everyone.

If a 1-shot role has a non-factional meeting and chooses something other than no one in that meeting, they lose that meeting in the future. Alternatively, if a 1-shot role has a reaction, it gets an "Enable reaction? Yes/No" meeting, which is dropped after a single yes. (e.g. a 1-shot bomb only kills their attacker on the Night they choose to activate.) Can be given to any role with a meeting or reaction.

Macho roles can't be protected from nightkills by docs/nurses. Can be given to anyone.

As for the front end, the icons of modified roles should probably have a top right overlay thingy similar to the second mafia team's red dot, but you might run out of pixels there.

I also have some thoughts on how to implement this in the game creator, but that's for tomorrow.