Well, I guess that is only when there is a whole lot of money involved. Usually, that is taken care of with a will. Now, if I had any worries about my wishes being followed, I would put something in my will as to the effect that: If my wishes are not followed as to my life's ending, then my money will be divided equally among those members of my family who wanted to follow my wishes, and the money that would have gone to the one or ones who did not follow my wishes will go to my favorite charity in their names. ;)
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.