Agreed on the Battery, alternator and reflector, but wiring is safe if installed with a proper wiring kit + relay + ceramic holders.
100/90W is not approved? Are you sure?
Please check page no 166 in this PDF file.
FYI, HID on a normal reflector (designed for regular halogen bulbs) is neither safer nor approved. HIDs generally go with projectors (unless used with specially designed reflectors + wash mechanism)
I said HID is safe because it runs cooler then high-wattage halogens hence it won't damage the reflector, battery, alternator or etc. This is what I know but I may be wrong too. However, there no rule about HID is whether approved or not and some cops charge fine.