Have additional 12-volt power outlets in a couple of places. These could be set to be always on or turn off when the vehicle is off. A plus would be an option to have buttons to turn the outlet on/off as needed.
This would be useful for lighting, dashcams, or a fan in the back if there is a pet in a cage.
Perhaps even an outlet for extra high beams (for whenever someone produces something that will work with the Tesla S, perhaps in the nosecone) that is controlled by high beams being on.