I don't have time to join, but I like this idea for a Jam! It looks to me that it depends on the game.
My ideas were something like:
- Platformer/hack'n'slasher: if multiple buttons are pressed, then excellent - it just means your character does more attacks! Basically what we called "button mashing" when playing Tekken back in the day.
- first person: voice controls, to control the character, it would probably need to be a bit slower and give time for the voice stuff to happen.
While my hands work fine, I know that my wife has small hands with limited range and can't use a game controller or keyboard properly, so any game with too many buttons won't be good for her. She can't even press W and Space at the same time. But, the theme is "hand tremors", and interesting to consider these once you start looking into it.