Since joining lobbies from 'custom games' menu breaks balance and is considered an issue breaking matchmaking I suggest that people should have only limited time to join, only at the beginning. I imagine that it would be first 30-60 seconds of lobby excistence. Then people who decided to join their friends could wait in spectator zone and join after match ends and maybe it would make the matchmaker work better.
Of course this wouldn't apply to the custom-made lobbies (before setting it to find people from matchmaking).
