I think it's deeply irresponsible to create a device which can drive in 90 or 95% of scenarios. It's just a way to fool humans into killing themselves.
If the system is even a few percent better than humans then it would save thousands of lives when widely deployed. Musk has made this argument many times. Basically don't let perfect be the enemy of better. But if the vendor is legally liable in each case then this software is untenable.
If you're actually trying to increase safety, the right things to build are computers to supervise the human driver, and not systems that require a human to supervise the computer driver.
If the human drifts out of the lane, nudge the car back in and beep, but don't prevent the human from intentionally going over the lines.
If the human appears to be driving into an obstacle, beep and apply the brakes, but allow the human to override.
If the human isn't paying attention, beep, then turn on the hazard lights and slow down / try to find a safe place to pull over.