VBR,
I half heartedly agree with your critique. There are some aspects, such as a proper flag system that would add to the Gran Turismo series. But being too technical will make the game lose its mass appeal.
If you are looking for a far more authentic racing experience, you should consider Simbin's GTR 2. GTR 2 is a fairly old game of the PC, but with a high end PC the graphics are still enjoyable. The RACE series of games produced by Simbin were garbage, and thankfully Simbin
announced they are producing GTR 3 (returning to hardcore sim racing) later this year or 2012.
But GTR and GT are in on two different worlds. GTR 2 is very hard to get immersed into for most people (a steering wheel is a must), while on the other hand all you need is a DUAL SHOCK 3 to enjoy Gran Turismo.
Never the less, the GT series is fantastic and their is no reason to mess with a formula that works and is accessible to a wide audience. Kaz essentially created the sim racing genre with GT 1, I think the man knows what he is doing.