I can confirm that it is remarkably frustrating, trying to find that spline if the wheel is off centre, so much so, that I always make a point of keeping the wheels dead ahead when removing the s/wheel.
Back to the immobiliser question, most insurance companies now ask for one to be fitted, which is a pain if you don't want it, for all the points already mentioned, ie they are a pain in the a55. So, how about a secret switch? Cut a wire somewhere, and insert a switch, easily reached from the drivers seat. The alternative, is to fit a big red batterey isolater key, and remove it when leaving the car, the chances of someone having one are fairly low. You may want to hide a spare one somewhere though in case the first is lost?
