Put in a match making fix that doesnt let a game start until teams are filled up or only have a difference of two players. Then make it so that only a one for one join basis is allowed. Taking longer to get into matchs is way better than constantly getting one sided blow outs on hyper under populated teams.
https://bhvrmtl.zendesk.com/hc/en-us/community/topics/200175666-Feature-Requests Would absolutely upvote btw.
I had a basic idea that may also be an interesting fix for the issue if the MM cant balance it out... turn a problem into an advantage... https://bhvrmtl.zendesk.com/hc/en-us/community/posts/255631086-Balance-and-elite-captain-concept
But people are already complaining the queues are VERY long and the fact that the playerbase is decreasing is not helping your idea.
unfortunately exactly same system is already in place and it doesnt work since ppl leave matches and you cant stop them from doing that. Current imbalance is 3 and it wont let you join if there is more. There are some exceptions, however.
A large portion of those people are ones that either join into an already lopsided match or join in late to a game that is un winnable. Many people would would rather just wait for a new match than play an unfun stomp fest.