I'm down for the idea, but my teams are locked at 70 and 80 for the series I'm currently doing. I doubt I'll be hitting top-level anytime before the release of WoD.
Facing off against another level 70 or 80 team is just as exciting as 90s vs 90s! Levels are not meaningfully restricted as far as I can tell.

As long as you're in the chat, though ..

But, really... If we do choose a more-centralized server in the Chicago datacenter and people want to play, then they could just re-roll.
I think people would generally prefer not to re-roll or pay for server transfer just to participate. I dunno. If it's exciting enough then yeah I can re-roll or transfer wherever for WoD, personally.

Unfortunately, there is already a larger group of boxers who had migrated to Kil'jaeden over the years (maybe not so large anymore?), but that server is located in the Los Angeles datacenter where people playing from the east coast might get screwed on latency/internet traffic at certain times. Even when I was playing on Proudmoore (also in the LA datacenter) I experienced lag during peak times and is one of the reasons I moved to the Chicago datacenter.
Probably the best point in your post. I have teams on Shattered Hand in the Ruin battlegroup, screw Bleeding Hollow! My main teams recently have been on Kael'thas in Rampage though.

While on that topic, EU should probably have a chance to participate too. I think a lot of boxers there are already on like 1 or 2 different servers anyway.