[eluser]wiredesignz[/eluser]
I considered using a pivot table when I started development, but due to our site requirements I decided to go the lookup (SETS) method.
We also have an online Dealer backend for adding cars manually or editing existing car details where we have to populate about 20 dropdowns with the different feature groups and match the selected items to the existing car.features data.
We do use a data import migration script. In fact its a database driven system where each clients car data columns are initially mapped and provided with data translation functions as needed.
I have enjoyed this discussion too, cheers.