There are many ways to lose even more weight on the Z. Every little bit counts, and adds up. However, again, you are missing a very simple point that its not simply about the total weight of the wheel. It appears the dynamics of a heavier wheel with other heavier unsprung items has detrimental effects on handling overall, a phenomenon that can't be replicated by adding a 20lb bookbag to your trunk.
Arguing from the viewpoint that we are not all Sennas bloodline is a foolish and self defeating stance to take. It has no bearing on the science itself. If you want to go there, why drive a fast car at all if Danica can drive a Pathfinder on a track and beat you in it with a trunkful of midgets? Just give up, kill yourself and burn the Z. Dibs on the wheels :)