And the forum thread that mentions the idea is actually full of great BG ideas-- a Team Deathmatch BG, multi-team CTF, and even an escort battleground. There's already that kind of thing in AV (you can run the quests that summon an NPC for you to follow around more than escort), but it would be neat to have a BG where you had to get an actual player from one place to another. Or maybe they could do it with an NPC-- run it in the Caverns of Time, and have the player escort someone in the history of Warcraft. Like Durnholde, but with players instead of an instance.
The other neat tidbit from this thread is that Ommra winkingly mentions siege engines as something she'd (he'd?) like to see in the BGs. So whatever news comes out about what's new in the battlegrounds, it's a pretty good bet that siege engines are almost upon us.