Don't misunderstand me here: I don't mean that you can choose who is going to be the impostor on the next game, I mean that you can choose whether or not you want to be ELIGIBLE to be chosen as an impostor after a random selection.
Some people, like me, have much more fun as a crewmate, trying to find who is the impostor, because playing as impostor is very stress-inducing, harder or more frustrating. Being able to toggle a potential eligibility (although confidential) could help with lobbies made of friends who are simply here to have fun with buddies, and I know I'm not the only one.
It's nothing much really, as it could be a disabled feature by the room owner, but I think it could add some flexibility to please even more people who love the game but despise the impostor role.
TL;DR: A feature allowing people not to be chosen as an impostor would be a great addition for casual players who don't like playing as one.