I have a few ideas.
-Have skateboards
-Different types of dirtbikes/four-wheelers
-Be able to aim while in a car or on a bike.
-Be able to challenge people to races (Have street racers driving around)
-Be able to select different/change appearence of charactors before the game starts.
-Be able to change facial expressions.
-Have a dragrace stadium.
-Be able to pull willies in some cars
-Have willie bars on road bikes (optional)
Thats all I have for now