DYI auto buddy works great. No nag
I'd imagine any sort of identifiable improvised “auto buddy” device found after an autopilot enabled accident would open one up to significant liability. It'll be presented as premeditated defeat of an essential safety feature. Whether or not the device contributes to the accident, it'll be presented as evidence of inattention and blatent disregard for public safety. They'll bring up the beta status of the software and the critical importance of driver involvement. I haven't examined my auto policy but I'll wager that intentionally disabling safety features would be grounds for nonpayment.
I understand the annoyance of the nags especially when one is holding the wheel and still gets the nags, but if one does decide to use a defeat device, it should be well disguised as to purpose and it had better not be on the steering wheel after an accident. One should not leave any discoverable records, and one should tell no one, and not use it with another person in the car, lest that person be subpoenaed.
If there are deaths, there may be criminal liability as well.
I was talking to a lawyer once and commented on the lack of science courses in the legal education process, specifically regarding logic of cause and effect relationships. I was told that legal requirements “are different”, they merely have to show two things happened and there was no requirement or obligation for demonstrating actual cause and effect. This went against what was taught in every jurisprudence course I've taken. Companies have been ruined through damages awards without scientific basis, and it has been proven later there should have been no liability. Still, the company was bankrupted, the lawyers got paid, and the cause and effect part of the process is now just an ironic historical footnote.
Is any of this likely to happen? Of course not. Along the same lines, though, it is unlikely I'll be involved in a major accident but I still buy insurance.