It's a game yes, a game of war. Pick a side for Cyrodiil or BG it up with your pals, we have that now.
I wouldn't mind a per campaign choice of faction, since I prefer to play on one character anymore. Even that doesn't really solve a problem though. It's not really a problem in my opinion. AD needs better coverage to even out, and I fail to see how this would solve that problem.
Currently i log into whatever factions scrolls AD is raiding in the morning to kick as many of them in the behind as hard as i can.
I think the game could have worked with faction lock if it had launched that way. You can´t retroactively fix it without very high effort and faction changes etc pp.
Except the game did launch that way........it used to be that what ever toon you made the campaign home with was the only alliance you could home other toons on. So my EP had to be switched out of the campaign to allow me to use another alliance toon.
While i feel it was a better system it wasnt perfect.