There should be an accessory option and a working radio (which would play from either the CD drive or from mp3 or any radio station from the internet) and for the dashboard, more lights that would turn on when you first start the car like the airbag light and ABS, etc.
Why stop there? What about actual working doors/trunk lids/etc? There are a lot of neat things that would be great if they added. I hope they get around to it. It would help my immersion.