Nope you haven't got what I'm saying at all, you keep refering back to the existing premium car list. What I'm saying is that if PD had chosen not to include standard cars in GT5 then they almost certainly would not have picked the 200 odd cars they did for the current premium list.
As such you need to imagine a clean sheet of paper for the premium list, and its more than possible to have a good balance in 200 - 250 cars, take the S2U car list as an example....
http://wiki.nfsunlimited.net/wiki/SHIFT_2_Unleashed_Car_List
...now I'm not saying that's what GT5's premium list should have looked like, but it does show that a good balance can be had without the need for 1,000+ cars. Keep in mind that
GT3 had less cars in total than GT5 has premium cars and still managed a reasonable balance (and without the advantage of being able to update via DLC).