I don't see how one could make a car seat that will absorb the energy that is transmitted to the head. The whipping action of vehicle movement will still impact the brain.

There are already air-ride seats and other suspended seats used in big rigs. They reduce the vertical component. Kenworth uses both seat suspension and cab suspension to reduce the impacts to the driver.

Cars are designed with crumple zones to absorb longitudinal energy transferred to the cabin. Airbags are designed to handle much of the rest. Side curtain airbags help with side forces.