Maybe just a difficulty meter indicating green (1-5), yellow (5-10) and red (10-15) for avg level in match? then no need to sort, just get the right colour and hope it doesn't change much from it before match starts?
I'd prefer a confirmation box, like an "are you sure?" thing. That way i could go into the match lobby and still have a chance to see and decide if i want to join that match or not. Take my peek without having affect on game before being sure about joining or not. Would mean shiptypes, builds etc could be checked before going ingame if it was running already, too.
friend colour for matchlist sounds good.
for mic it could just be a X on speaker beside player name, if voice disabled ingame?
I'd want to see a connectivity indicator. Ping bar/number/health. For match only or even clientbased.