IMO people should be aloud to make their own teams and duke it out with each other as long as both teams are both even on terms of skill and gear and both teams are actively fighting to win. Anything else to me is considered wintrading/boosting. That being said, while doing this i would expect them to accept any other challanger in the queue. (like how my group encountered 2 other groups during our session and excepted both pops without delay)
But like others have said if my team proceeds to get steam rolled 30secs in (twice :c) , Kudos to the other team but heck no am i gonna stay.