If a buyer opts for the Full Solar option, it appears that the rear window is going to be almost totally covered with solar panels.
Would it not make sense to remove the Glass, assuming that is what will be there. Replace it with composite and lose the weight of the glass window. That would also make it more difficult for people to see items in the storage area. If you really dont want them to see, there could be a pull down to block seeing from the other windows.
You may even be able to slide in some extra panels and up the daily gain in charging.
I think there is a rear view camera already.
I did see that they are already looking at replacing glass with composite, but in this situation, it is just body color. No extra cost for transparent composite.
A potential solution might be to set up something like a horizontal camera obscura that uses lenses to project onto a mirror internal to the vehicle. Maybe this would satisfy the regulators? There is still technically a mirror present, and it is an analog solution. On a minus side, it would complicate things a bit (designing optics and mountings so that image is aligned correctly over time and temperature range, image is not inverted, address the safety issues associated with potentially having eyes and lenses and the sun on an axis, ensuring optical components are mechanically coupled for syncing vibration, address risk of getting condensation on the optics, setting up reliable supply chain for new parts, etc, etc). On a plus side, if it is an ideal solution, then use it for all models and get rid of the rear glass entirely (not sure rear glass serves any other purpose than for rear vision?)