So first of all, this looks great. I was in debate between these wheels and the inductions - spending an extra $2k is hard to justify. What would happen if you plastidipped the edge with the cap off and then put the caps back on?
Just to address this more directly. He wouldn't want to plasti dip JUST the edges of the wheel. Plasti dip is only nice an easy to peel off when you have full consistent layers. If you just spray around the rim of the wheel (just the part which is showing in the pics) you would not have a good layer, and it would be a nightmare to peel off.