Take into thought some figures:
The CF trunklids cost about $2000 to develop for us and sell about $600 each, and a trunklid is a relativly smooth plain suface with few curves and contours to it.
A body kit will have the sideskirts, front bumper, and rear bumper if just a basic kit is made and not the wide body you're thinking of, the design, even if simple would cost so much money to develope and then the cost of the kit would easily be in the thousands of dollars.
Although a cool idea i don't see if happening unless everyone suddenly has thousands of dollars to invest towards this.
