I was gonna close this thread immediately when I heard about the competitive mode and new matchmaking, although I want it, I was like "Wait, this is Valve, they'll find a way to make me lose faith", glad I kept reading and saw mp_highlander.
Also, I don't think the matchmaking will require that many servers. If it was 6's, then yes, but since it's HL, that's 18 people a server, and a big part of TF2 players might not play it and stick their pubs/trading.
But would restricting this mode to people with a certain amount of hours be a good idea? That way players with barely any TF2 experience or knowledge can't join and possibly create a disadvantage for the team. This would also help limit the amount of people that can join matchmaking, and require a bit less servers. I think maybe setting it to requiring 100 hours to play would be fair. This would also help stop people making a new alt and trying to matchmake and try to stomp players that are lower skilled. They have their own kind of guard like this for Dota 2.