Yeah I agree, that would be fun!
The event would take quite some time to finish though, with monitoring every single group. But it's a great idea!
I just came up with another suggestion but with the same concept. What about, horde VS alliance. Who can finish X raid first... Let's say ZG or MC. Pick 40 people and speed it. Like no time for slow loots, ress, afk's etc.. Just pure speed run with 40 of the factions finest raiders. The problem would be the prize for the winning faction. Though I kinda figured out a soloution. The winning faction will get quite alot of diffrent potions, just mixed. (everybody in the raid is probably in the same guild aswell, and who doesn't need potions!

)