I don't think that will happen ... ever ...
They just juse that as a simple lazy ass way to disable cheating and corner cutting. Simply hate, that there is almost zero grip on grass and once you're off, you're OFF and AWAY. I know that grass has very low grip, but there still is some. Anyone, that has been racing on a track and has had an off could tell you that. In GT5P - when your car is off it is also out of control and you can't do nothing about that but sit on the brakes and hope that you hit something and stop soon.