I get what you're saying tka, and I think it's a good idea. With the sheer volume of cars in GT5 it's inevitable that some of them aren't going to handle quite like their real life counterparts.
The biggest obstacle I see in what you're proposing however? Finding people who not only own the cars in question, but who also have the skill and experience with them to accurately translate that to GT5. I mean, I've driven a Sentra for the past few years, but because I've never driven it anywhere near the limit, I couldn't really tell you how it would behave in a racing environment.
There are, however, some very knowledgeable people on this forum. So perhaps a few cars could be done at least.