Interesting @howo. This is like writing your digital will through code. Have you looked at https://www.eternitas.io/ before? You can write your will on the blockchain without the need of any third parties like lawyers or friends or family members who could collude with each other. :P

But you have listed down some unique solutions to the problem like sending different parts of the keys to different people. Make it a bit of a treasure hunt. Would be fun to see all that happening from the heaven or probably hell. xD