Hi Friend,
That's perfect modification using existing AC setup.
I've read on internet, some LED Bulb driver do support AC volt, it's just a matter of adding extra components of bridge rectifier by the manufacturer. Since these LED bulbs are flooded by Chinese manufacturer don't know which one is genuine and supports both AC/DC voltage. BTW we have a juggad for it :-).
I had installed HID kit 2 years back, but it sucks battery like a hell. Later I've to remove that because the HID ballast was conk off. I had replaced HID with LED Projectors, though it is directly connected to battery but LED's requires minimum current so not putting much strain on battery. It's working pretty good.
Hope, I may go for the same setup in future because AC headlight connection from alternator is idle.