One suggestion to solve this imbalance would be to implement a stack vs stack matchmake like in CS Go. If people 5 stack they are more likely to get put in a game where the other team is stacked as well. If enough players play in large parties they can easily implement it so that the system pits them against each other. Of course sometimes it won't because there won't be enough said parties but that is one solution to your point. I am not well versed on how easy it would be to code the matchmaking system to do such a thing but if it is a possibility it will almost fully eliminate the problem, at least in my eyes. There are plenty of ways you can counteract a well organized party and it all comes down to making the community play together more and forming social circles, but not at the expense of the solo player of course.
That's a good idea. From a programming perspective, it's certainly possible. The question is mostly how it affects the matchmaking time and quality. If you enforce it too strictly, parties may spend up waiting for a long time, because it needs to search for that perfect 8 vs 8 line-up.
If you allow for a less strict ruleset, then that may mean faster matchmaking times, but the matchmaking quality goes down. What I mean by that, is that you may end up in situations where you have to accept matching a party of 4 against a party of 8. Alternatively you'd have to compromise on ping or map preference.
It certainly doesn't have to be perfect though. I'm perfectly fine with a ruleset that isn't too strict, as long as it leads to a decently playable experience.
