I'm definitely biased towards farts, but all of these sound fun. I don't think I quite see in my head what the first option would look like, but I do like bullet hells and it certainly sounds interesting. a chill fishing game sounds fun as well, but the stealth fart game I think is what I would be most interested in.
for the first idea, basically imagine undertale's battles, but you have to survive for a certain amount of time during it, and after each battle you get to choose cards that change stats n such.
and yea, i think the stealth game idea could be the most interesting, and im sorta surprised no one has done something like that yet tbh (or maybe there has and i havent seen it yet)