They should offer a complete guild transfer for 100$. So you can start with your Alliance guild on a new realm as a Horde guild. This would be a service many guilds would use. Or a 30$ "complete account transfer" so your 11 characters would all be transferred and turned into the other faction. Right now they get 0$ from me because it's way too expensive to pay for every character to do that.
PS: I'm playing since 2005 (EU launchday), seems to be very important here