I would certainly take part in an such event if it would come along.
Seeing how Azeroth now is pretty much primed for such events, i'd perhaps suggest making the events take place in Azeroth instead of Outland (which is pretty much deserted). If you arrange the events with some loosely attatched RP story to it, im quite sure you'll have several horde guilds that are willing to help you with it.
Warsong blades and the Korkron Assault would be two of those that i can pick from the top of my head. In addition im quite sure we'll have quite alot of other "specially interested" people aswell(me and the like).
I wish you good luck with this, i've been crossing my fingers for that Cataclysm would bring more world PvP.
This sounds really awesome. I saw a screenshot about 40vs40 yesterday on another server and thought we on SSL should do that too.
I think some in our guild might be up for joining and to fight for the Horde!
Just tell me when you plan to do such a thing and I will try and rally as much guildies as possible :)