This idea has been forming for several reasons, including the Warcraft 5/15year anniversary, a recent Halaa PvP session (which was completely epic, and was what world pvp should be), and the upcoming Cataclysm. Hang on folks, it's a long read, and has lot of flaws, but perhaps you guys have a few ideas of your own to add to it.
Like Wintergrasp, it would not be instanced. Unlike Wintergrasp, the battle never stops. You just fly/port/whatever into the zone(perhaps that could be a new mage portal spell to take you and your group back to base). Upon entering the zone, you are technically grouped with everyone, for sake of everyone getting credit for kills. Here's where it gets tricky folks, we're about to get a little complicated, since a whole lot of PvP ideas from past battlegrounds and the like will soon be combined.
The Alliance and Horde would have a base on the east and west sides of the zone, with a coast on the south end, and the obligatory steep mountains on the north. You'll see why the north and south geography is important later. In the middle of the map there are four towers that can be captured. When captured, reinforcements will arrive to shoot at enemy player passing through. Get to the top, click the banner, wait a minute, and voila! Your tower.
Now comes the Warcraft 3 part. A random player will be assigned to be their faction's "zone leader." They will keep this title (and their name will be at the top of everyone's screen) until they leave the zone, log off, or click a button to relieve them of the title because they don't want it. At this point, another person is randomly given that job. Why wouldn't you want that job, you ask? Because it's a headache. You're in charge of many, many actions. First and foremost, you will be assigning important jobs to others.
The first job you can assign is the Base Designer (for lack of a better term). He builds your base. You see, the base is essentially a roped off part of the map where you can build anything you like, or rather, what the base designer likes. The only permanent part of your base is the main castle/hold in the middle. The base designer has access to a number of buildings he can choose to tell the peons to run off and make. All of them have a strategic importance. Barracks will produce a steady stream of soldiers to patrol around your base. Arcane sanctums will create mages to man any of those four towers that you have captured, who will do more damage than the standard archers who usually appear.
Once the base designer has built the aerie, the zone leader can assign another job: Patrol. Anyone assigned patrol will be given a free epic flyer as long as they have that job. Here's the catch: they can't dismount, and as such, can't fight. Their job is to scout out the zone safely atop their flyer and search for any enemies, who they can use a special button on their vehicle interface to mark and yell to the heaven's about. Safe, but unwanted should only ten allies be in the zone, since they can't fight now.
The workshop works much as they do in WG and IoC. Go in, get vehicle, go tear down the enemies buildings. You can also place two towers within your base. I'm sure there are other buildings you guys can think of, I'll leave that to you.
Next is the gold mines. There are three on the map, one close each base with one in the middle. You should have at least the one near your base, and if you can capture the one in the middle, troops are produced quicker by your buildings. If you don't have any because the one near your base was captured by the enemy, l2play. Similarly, there's a mine in the center that will make stronger buildings for whoever controls it.
What I really miss about old AV was the fact that you could do repeatable quests to upgrade your troops, a useless idea these days. We're bringing that back. Go get some leather off those mobs over there. Miners, bring in your ore for the best possible armor. Go reign in some horses so a we can create knights from the barracks. We're gonna give the opposite faction second thoughts about fighting our NPC troops.
Now for my final thought (and much thanks if you've made it this far, I know it's sloppy, we're almost there), we're in a war for resources and survival! The Cataclysm trailer said so! Besides, I think it would be great if PvE players got a benefit from PvP players in more of a way than they do in WG. As such, its time to bring back Grizzly Hills PvP, an idea I wanted to like, but wasn't fleshed out enough. In the north there's a lumber mill just like the one in Grizzly Hills. Capture it and you get access to lumber, causing buildings to be built quicker. In the south, there's a harbor. Controlling it is useless without the mine or the lumber mill. However, when you have the harbor and one of those other two spots, the ship will leave out with a cargo hold full of metal or lumber depending on what your faction controls. This will open up extra quests in other zones for people doing the whole PvE thing, since your faction has gotten their hands on some much needed materials!
I guess that there would be little way to win the zone, since the battle never ends (which I think is the core factor in world PvP and the failing point of WG). Perhaps give a buff to everyone on the continent if their faction can get into the other's keep and kill the NPC general, who will respawn in an hour but in no way hinders the battle from being fought? That and I wish I knew about more jobs that the zone leader could assign. Oh well. What do those of you who actually had time to read all that, what do you think? Any suggestions?