I think this system works alright in large games like TF2 where you can juggle without disrupting everyone else, though note that TF2 has a server browser that the quickmatch doesn't fuck with and so I never use matchmaking myself.
The problem with doing this in Zero-K is that you will ALWAYS have to disrupt games to make the juggler work. There aren't enough concurrently occupied hosts to allow people to play things they actually want to play. The current implementation is like if after every map of TF2 it kicked you off the server and required you to join a completely different server with different people and different maps, even if you didn't use matchmaking in the first place. This would be the worst thing.
And the size-segregated teams hosts are ridiculous. Yesterday I was trying to play with Skasi and Harvey and juggler wasn't having any of it, because at the time people happened by chance to be in a small teams host. I don't think anyone would have minded playing 5v5 to accommodate the extra people, but they literally cannot do that without everyone leaving the room and joining another. And this isn't a "lack of play with friends option" thing. You want to play teams, and there's only a 4v4 small game? Sorry, you're NOT ALLOWED TO PLAY ZERO-K.
These are exactly the same problems as the last iteration of the juggler. I don't think you can fix this in a game of this size while maintaining an effective matchmaker. Just let players do what they want.