This idea has been floating around ever since we all realized there were two new opposing reputations in the Burning Crusade-- an Aldor vs. Scryer battleground. It would definitely be a fresh change of pace to line up alongside the opposing faction and have a chance to face off against your own friends and guildies. Of course, there's lots of coding work that would have to be done (as well as a little lore work-- Aldor and Scryer aren't exactly in open war at this point), but it would be a cool addition to the current battleground options.
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.