Or, a whole lot of bother. Or, an elephantine ego armed with tons of money and who really couldn't care less whether she gets written out of the will.
The fact that you are proposing all these schemes to stop what would have been unthinkable a bare few decades ago, should be a huge red flag to you. Slippery slopes slide on, the drain on Medicare becomes more and more tempting to meet by encouraging people to make the earliest flimsy-excuse-for-reasonable exit they can from this mortal coil, and it is a prescription for nothing but trouble.
Actually, I was not proposing "schemes." I was trying to explain a plan of action for folks to follow so that their loved ones, and not so loved ones, would know their wishes for end of life care. Also, we may not always be in the care of our own doctors at a time such as that. We may be in another hospital due to transfer because of need for more specialized care, or because we became ill in another state, etc.
Also, we may marry a second time later in life and there may end up being a problem with step children, etc.