what you could look into doing is setting up the reflector side of those as foglights, aim them at the ground...maybe use yellow bulbs and still do the how/high beam in the projector side of the lights so you only need 1 bulb/ballast on each side for the headlights. if you search on hidplanet.com they have forums detailing everything you could ever want to know about HID swaps, conversions.
I plan on running the bi-xenon FX35 or Murano projectors in a modified 7" sealed beam housing on my Z...im sure there is someone on HIDplanet that has done something similar to what you are doing