No, we don't need player limit changes to change the meta game.
We wouldn't be trying to deliberately change the meta game. You're missing the point entirely.
6vs6 TF2 is fine how it is (to play), but there is no growth (or very little), there is no support (or very little), and it is pretty dull to spectate for anyone other than a current competitive 6vs6 player (or a few randoms).
That is a problem. Without growth, the game starts to die off. Without support, eventually the development team stop fixing things. We are lucky the public scene still makes Valve some money. While the game is dull to spectate, we will have little sponsorship and few offline events.
We have a chance here to rectify this situation. Valve has opened a door suggesting they are willing to work with us. We could get the developers support back. At the same time, if we can make a game mode that public players are actually interested in, and have it built into the actual game, assuming it promotes Valve's money making mann co store (see part about getting developers support), then we potentially get some growth in our competitive community.
Not only this.. but with public players playing a similar game to what we play, they will have more interest in spectating us to see how it's done. They will learn from us. At the moment they don't care how Clockwork uses a scattergun because they use the shortstop in publics. NOT ONLY THAT, but with more spies, snipers, heavies, engineers, pyros, public players have an increased reason to watch us, because they are some highly popular classes in public play! More spectators = better sponsorship = more exposure = more growth = potential for increase quantity and quality of offline events.
And the cost for all this?
We sacrifice a portion of the current game we are playing. A lot of it will still play similar, but it would be the biggest competitive TF2 change to date. Is it all worth it? I don't know... sadly I don't have a crystal ball. The actual return could end up being minimal, we might not grow, the new meta might be even more boring and stale. Maybe Valve don't give us the extra support we hoped for?
One thing is for certain though, and that it that TF2 is going nowhere in its current form. Stay as we are, or go for gold? Your move community!