defective in this case means there was a flaw with the motor a manufaturing defect. Motors will reach a natural end of life and need to be replaced. this is not a defect.
Do some reading on clear solar panels. they exist but are still to early in development to be used. I think that is the way forward with EVs. all windows are solar panels and they are perfectly clear.
But as that is a ways off i think the front roll down window cover is a fantastic idea