Have you ever driven a car longer than 5 minutes? There is no way touch sensors in the steering wheel would be a beneficial addition. People switch hand position all the time. I'd dare say there isn't anyone who drives a car with a hand on the wheel at all times. Having the system disengage all the time would be ridiculous. I suppose you could put a timer along with the sensor, though. Still wouldn't stop anything. A person could easily rest a hand on the wheel and never once look at what's actually happening around them.
The right solution is to make it clear that this "autopilot" isn't anything more than an assisted cruise control, like every other manufacturer does, and people wouldn't think it was more capable than it is. Or simply let the dumbasses be dumbasses. It hasn't impacted car sales by any other manufacturer. Hell, there are some 30,000+ fatal accidents every year in the US with "regular" cars. Some are certainly manufacturer defects, but most are human error. Why should Tesla be held to a different standard than all other manufacturers?