Rather than individual cars that we lust after, I think perhaps it's time for PD to bring cars out in packs that all have racing legitimacy TOGETHER. In other words, cars that would have raced together in tightly sanctioned series when they were current (or even now).
While bringing them out one at a time, or in wildly different collections is all well and good, let's not forget Gran Turismo is a RACING game (until we have normal street courses, not racetracks, no-one can persuade me otherwise!), and the idea for collections of equivalent cars that would have raced together IRL just seems to make sense.
While liveries could be happily left off if PD don't want to pay licensing fees to the teams, spec-ing them to be series equivalent would go a long way to providing some good, close, even racing.
I own a Nissan Laurel ( model C32) which originally came with a 2L I6 SOHC engine and 4 speed automatic. I changed it to a 2.5L DOHC 5 speed automatic and it burns tyres shifting from 1st to 2nd so it performs well for a basic sedan hardtop. I can outrun most n/a cars. I would like to have my car in the game please.