Matches shouldn't begin if someone leaves
Everyone knows 4 vs 5 placers is a roflstomp. So if someone leaves or gets dc'ed, the match shouldn't begin, just like it doesn't begin if someone doesn't load into the arena.
Yes this means that people could exploit the system if they get matched with someone they don't like, but aren't those people already getting the leaving penalty, so they're not able to requeue for 30 minutes?
I'm not sure what happens after that though, is it just that they're penalized for 30 minutes each time they leave? Or does the penalty increase every time until 24 hours have passed?
If that's not possible, I would at least not penalize the other four people by costing them a star just because one person left..