What I'd like to see in a "training mode":
back in MotoGP: URT 3 (I don't recall any other game with that feature) in training mode you could quickly move your bike around the track and place it in any spot you wanted, which was handy if you wanted to practice a particular section or even a single corner.
I find myself struggling in GT3s with Nords' Carousel and being able to keep driving over it without the hassle of spending 6 minutes to go around the track or stopping, turning around, going back and doing it again would be helpful.