Don't know if this is the place or not, but i've got a suggestion for later down the road:
Rivals.
Two guilds could pick each other for the matchmaker to set them against each other. It would only work if the leader of both guilds lists the other, or you could even set a list of guilds you'd like to be set against depending on availability. I'm part of a mega guild network, I think there's three or four of us now, and it would be so much fun to set a rivalry up between the sub-guilds. It might also let the really dedicated wvw guilds set themselves a proper challenge, even allowing for them to coordinate major rivalry battle nights.