drivers ... able to immediately take control of the wheel
What does "immediately" mean ? The number I've heard mentioned is within 4 seconds. Which is quite short to asess all of the external conditions from scratch. So, sort of ebgs the question as to why have the AV ?
...ensure that in the inevitable future car crashes that will take place with these vehicles, it can be shown, clearly and legally, not to have been the fault of the software....
An invalid presumption that it will never be the fault of the sofware ( or, more accurately, the system )