If they introduce a mechanism where the manufacturer only can unlock the car, it would mean that they will need to be involved in all kind of disputes people have over the ownership or usage of the car. You will also have people telling you that you don't own the car as with the case of the some agriculture manufacturers that lock down their systems against unauthorised repairs.
I'm more in favour of leaving the police work to the police, let's not integrate the law enforcement and manufacturers. There's already interest in disabling cars when authorities deem necessary. The problem here is that the authorities might not be or may not remain your favourites.