The solution would be to make a system that senses when it is in drive, and provides a do not start signal. Thus if this sensor fails someday, it is a failure

The solution would be to make a system that senses when it is in drive, and provides a do not start signal. Thus if this sensor fails someday, it is a failure like any other than now technically breaks a law.. just like a failed windshield washer motor would no longer be compliant... But the vehicle can still technically start. The owner can then decide if they want to fix the issue and have a fully federally compliant car, but it isn't bricked until they fix it. How would you feel if your windshield wiper motor failed, no rain in sight, and you could no longer use your car? That's how users feel who can't use their car because a park position sensor failed.