DollyI said it before and I'll say it again:
This is all too late, 6v6 is IN THE GAME, this won't amount to anything and even if it did we know how valve are and they would no way go back on what they've done.
The 7v7 format doesn't even make sense as you're either just plonking a heavy into the teamfight which makes things slower, or a sniper which is a lot of just waiting around for him to get kills, which is one of the worst and most hated parts about highlander.
If anything 5v5 would be better since it would allow people to bust through areas easier and the roamer role wouldn't be set in stone, but that's theoretical, this shit is just painfully pointless and isolating new players even more, which is one of the biggest problems we have in tf2 right now.
If it was just 7v7 it would still be cancer, but it's 7v7 class limit 1, so not only are you putting retarded shit like heavies in, you're throwing multiple offclasses into the mix for no reason.