Yep - Dan just convinced me to skip the HID thing until Bosch or Hella make a 124 HID headlamp (like THAT will ever happen). I would like to see Mike's modified reflector, just because I can't picture in my head what he did!
About making a kit, I think I could do a kit for the 124.1x3 (like Speedy's and mine) since I have one to play with, to get the mounting locations correct etc. I'd be nervous about making a 124.036 kit (500E) because I don't know where to tell people to mount the relays. I'd want to have step-by-step, idiot-proof instructions. Some tools would be required (crimper, preferably controlled-cycle; and possibly a soldering iron - depends how you want to do the final termination [direct to bulb or just to headlamp 6-pin conn.]).
Neil's setup looks pretty clean, I like that. Neil - do those Hella relays have built-in fuses? Hard to tell from the photo. You still need to fuse back at the battery for short-circuit protection but a secondary never hurts. The MB connectors are a nice touch too.