One of my GS customer(white, not you GSXOTIC) had that set up......It's definitely possible to do that but the result was just ok, not very impressive......You should've seen GSXOTIC's Raybrig HID foglights, they are AWESOME So bright and the color is sooooooooo nice~
It can be done.....you just need a 9006 conversion kit.....however, you may need to lengthen the standard power cable that comes with the 9006 kit because it will be a bit short. I had to extend the power cable for my low beams.
Another issue is where you gonna mount the ballast for the HID fogs.... since the cable between the ballast to the 9006 re-based bulb is about 10 inches long....you may need to secure the ballast somewhere close by (in the bumper area...maybe behind the fog housing?). You may need to remove your bumper for this.
I dont think you need to worry about the length of the HID bulb in the fog housing....it should be the same length of a halogen bulb. The only thing I'd question is if the ground return wire will be facing down in the fog housing.....i remember the fog halogens sitting at an angle. If the ground return wire is sitting at an angle, it should NOT affect the fog beam pattern much since the fogs point downward anyways.