Adjustable suspension would add an entirely new aspect to the handling of cars, as well as static appeal. My BMW E46 is nearly impossible to control, and i think if i were to make the suspension as stiff as a rally car's, i would be able to use the throttle around the corner. Lowering and "stancing" the car adds appeal as well. Yes, you can make a car ricey just by stancing it, but rice is nice. I would highly reccomend adding this feature + rally cars + off road tracks + toyota + bodykits all in one package dubbed "The rally update".
Many thanks
-Curlyawesomeace