I checked this. My human brain can see when a human has hands on steering wheel with high confidence, without seeing the wheel or the hands, so I think the cabin camera would be fine for determining hands on steering wheel with high likelihood. Just have to have a super NN to do it. (I don’t know whether such good NNs exist.)
Tesla Model 3 and Model Y come with an integrated passenger facing cabin camera, Tesla hacker green unlocks the recorded clips (videos, details).
www.teslaoracle.com
Anyway Tesla should do this. Force both hands on wheel most of the time. No torque sensor. Go for it.
Would work fine. The way you know if it can be done is to have a human look at camera output and determine when the driver has hands on wheel and is not distracted. If that is possible the car can do it. At some point (may require step change advances in AI or solving AGI).