A feature that I would like added would be a track builder. It would include different types of roads (concrete or asphalt), road barriers, scene settings, weather settings, color settings, race type (meant for drag, circuit, endurance, etc.), road markings, start/finish settings, etc. Another thing would be a way to get to the custom tracks. If you could put it in the single player folder, that would be nice. To race on them, the tracks should be located w/ the in-game tracks on free play and split screen.
This would be wonderful to add in the next major update.