After my first autocross, a great idea dawned on me. Why not include a "autocross" editor in the next Gran Turismo game. Since the game is not about racing, but instead driving, it would be awesome.
The "layout" would be:
One flat lot. Black tramac, some trees for a background, or shrubs maybe.
On this lot you can place cones to create whatever shape and size "auto-x" course you want within the lot.
Can it be done? Definately. There are at least 2 PSone games with track editors and GT3 has cones in it that are independent from the track and can be knocked around.
I think it would be neat to construct your very own tight auto-x course where say 2nd gear might be the max and settings play a large role.