It would be really useful to have a free roam area to learn how to use the handbrake, test the turning limits of vehicles, see what effect your tuning has on performance.
A simple oval/bean shape track surrounding a carpark/skidpan that includes the main surface types in the game. Gravel track, asphalt carpark then choose wet weather to get a variation that might include ice or snow.
Crucially no timers to restrict how long you can drive and quick access to tuning without trawling through menus. Drive the car, hit Esc, change a setting, leave the menu and drive on.