Planetside 2 reminds me a lot of WvW in more than a single way. I think you guys should give it a try it might spark some good ideas for GW2 WvW.
I know it is a FPS but the similarities lie in the “capture the keep”, “siege weapons” and big consistent maps that both games employ plus PS2 has a pretty solid system to reward players for supporting, destroying enemy siege and defending facilities that encourages engaging on defense and support activities.