I guess I just don't get the addiction to modifications
Seems to me it is like that old joke where a guy asks for directions to XYZ, and the farmer says something along the lines of "Well, if I was going there, I wouldn't start from here".
If one wants a car that is very individual, why not start with something unique? I like my X5 very much, but there are lots of them (4 on my street, 4 on the same level in my small downtown parking garage). I assume that there are similar numbers where you all live as well (well, maybe not motordavid).
And if the goal is to go faster, accelerate quicker, stop better, then aren't there any number of starting points that would get you there faster/better? Having multiple vehicles makes more sense to me than supercharging an X5.
I do understand installing factory-engineered options that were not in the original build, and things like the IceLink. It is the custom stuff that I don't get.
Of course, ESS makes a supercharger for the Z4 as well. Now that would be fun. Of course, if I wanted to spend that much I could get a nice Porsche, and follow my own logic...