New battleground: Caverns of Time: Blackrock Mountain.
For those of you who weren't around for vanilla WoW or were on a PvE server and might not have noticed: Blackrock Mountain was a natural PvP area. Until the release of Ahn'Qiraj, there were only two 40-man raids: Molten Core and Blackwing Lair. Both were reached through Blackrock Mountain. There was also a level 55+ instance which people ran frequently to get FR gear for those raids: Blackrock Depths. Finally there was Blackrock Spire, which was effectively two instance: Upper and Lower, both 58-60. The general idea is that two raids and three of 6 or so end-game instances were all in once place.
The result is that everything from 5 mans heading to BRD, 10 mans for LBRS, 15s for UBRS, or even 40s for the raids, are all going through a single area. Even better, they were effectively channeled to a single spot within the mountain, a rock that connects to a chain: up is BWL and BRS, down is BRD and MC. It was not unusual to see constant fighting, ranging from 8 people to 80. Or more.
Like I said, natural PvP. I don't think Blizzard tried to do this. It was too perfect to be intentional.
Bring it back, in a battleground. The idea is originally by Iapetes, but he was talking to me and I'm the person with rose-colored glasses, so I stole it.
The general idea is that each side starts at a doorway and then rushes for the raids. Then they try to capture them as you would a tower in EotS. The new part is that capturing a raid and holding it for a certain amount of time gives stat boosts, reflecting the increased gear. However it can't just be a zerg to the best spots. If you only have low gear, you will take longer to capture an instance. The idea is that initial fights would be over BRD, but the loser might jump to LBRS/UBRS and try to get a leg up. After that it's a huge fight over MC. Again, the loser can retaliate because even after getting MC, the winner will still need UBRS and, should they happen to lose BRD, they will more easily lose MC. The idea is to mimic the old progression and to also add some complex strategy.
Oh yea, and don't forget the risks of dueling on a narrow chain down to BRD and MC. If you're brave, try the lava. Priests, welcome to the glory days of mind control.
You can get any raid or instance at any time, but there are buffs to speed it up.
BRD speeds up MC caps.
BRS speeds up BWL caps.
All of them give gear which will give its own small increase to capping speed but is most useful for the fighting. The higher the instance, the faster the gear comes in the order of BRD < BRS < MC < BWL.
Just as holding an area speeds up caps, not holding it speeds up losses (duh) but also slows the gear gain from the higher area. So don't think you're going to grab BWL and MC and live it easy, not having BRD and BRS will prove to be your undoing.
If this is too complex, just run around killing people, it's what most people do in the other BGs anyway.