This may be a little redundant, but a few suggestions(I know these would take a while to work out, if they're possible) :)
Voice chat in game for during meetings! Probably optional, since some people can't or don't want to use a mic.
A chat specifically for imposters that only they can see during the game! Would make it easier for imposters to communicate and coordinate kills. Of course, that could also be optional- a game setting that can be changed in the customisation settings.
A search function for games! Some people are specific about the types of games they want to join, and will spend some time on the matchmaker trying to find a server they think they would like to play in.
Last thing is adding the code to the "full game" messages so that players have the option of joining the next round if they do not know the maker of the server but want to play in it, since the matchmaker cannot auto update everytime someone joins.
Finally, I have no idea if this is the right place to put all of this so I'm dropping it down here. I'm very excited to see future updates for Among Us!