My 2016 adaptive cruise control already does this. There must be more to it than this. ACC will follow the car in front of me to a complete stop if necessary already. And then resume too.
My understanding is that in this case Mercedes if fully liable if something goes wrong - so you are allowed to watch a movie or read a book. If the car proceeds to crash into the car in front of you, Mercedes is on the hook, not you.
I doubt your liability is waved when reading a book while using the adaptive cruise control in your car.
“Like related Level 2 driver-assistance systems, Mercedes' Level 3 technology handles driving speed, following distance, and steering. In the meantime, it keeps tabs on a preset route and traffic signs and signals. The system can also brake and/or maneuver to avoid potential situations.”
So, it reacts to traffic signs, and can change lanes to pass slower cars.
I doubt your liability is waved when reading a book while using the adaptive cruise control in your car.