Sounds really nice but I'm still not 100% sure, that I got it all right.
For example: I have a Team with 3 people, who all have an average MMR of 2,5k, then we invite some 4th person to this team (seems that it doesn't matter, who that person is) and now start queueing and lose every match by purpose until at least the 2 guys from the original team have a MMR of about 700. Then we start queueing with our original team again and get enemies at 2k rating, maybe even lower and for a win we ALL get high increases of personal AND teamrating? And this is even doable until 3,2k? Sounds too ridiculous to be true

So, if there wouldn't be any disadvantages for the 2 people with the low MMR I would definately try this. Please confirm if I got all the information right and nothing mixed up
