I definitely agree with you on this one. I had an idea like this, too, when considering how much power the PS3 will have and much space the discs will have, I want some Dakar and Baja 1000 action. I'm Ivan Stewart!!!
The Baja 1000 would be fun. Its fun to have rally cross (thats basically what its been in the Gran Turismo games) but a point-to-point type of racing would be better. Something like the Targo Florio or Isle of Man would be pretty cool to. Dont know if that counts as a rally but it would be pretty cool none-the-less.