Well, like I originally threatened I have finished mounting E46 (audi/bmw) projectors with HID bulbs/ballasts. The projector shrouds aren't complete yet, but the projectors are at least installed. It's simply a modification to the reflector housing so it can still utilize the headlight casings own leveling bolts.

The nice thing about this setup is I won't have to worry about casting off glare from the reflectors of a traditional H4 HID setup (not that its terribly bad in the first place, and can be remedied with a proper glare shield), and I get that pretty vibrant semi-purple flicker when you view the fresnel lens at just the right angle.

I did fabricate a custom cut-off shield on the projectors themselves to accentuate the effect.

Here's my step by step, though I doubt anyone would be interested in doing the same.

The projector:

Opening up the headlight assembly (via boiling water)

More of the assembly open:

Cutting the opening for the projector:

Test fit of the projector in the reflector:

I cut out and reshape several plastic mounts from an electrical housing for the projector to mount to on top the reflector housing.

Using high-strength plastic epoxy and sanding the areas to be applied, I glued the plastic mounts to the reflector.

The projector mounted/screwed to the plastic shafts.

Another view of the projector mounted to the reflector housing.

All powered up to the ballast, testing heat/operation.

projector light hitting the wall. the camera is a little overwhelmed so you can't really see the distinct cutoff. Notice there is no light hitting above the cut off.

Reflector remounted back into headlight assembly. Ready for shroud around projector, then to be resealed with clear cover.