This would be difficult with the current legal system in most of the United States because of the rule against perpetuities[0]. Of course, jurisdiction shopping makes this easier in certain locales.
I observe there's a certain prejudice, in that law is written by the living.
The other ideas of cryptocurrency/escrow/private keys would escape the law... until you tried to spend it legally. You might as well bury gold in a chest.
[...] I don't know what this great think I'm meant to be doing is, and it looks to me as if I was supposed not to know. And I resent that, right?
"The old me knew. The old me cared. Fine, so far so hoopy. Except that the old me cared so much that he actually got inside his own brain - my own brain - and locked off the bits that knew and cared, because if I knew and cared I wouldn't be able to do it. I wouldn't be able to go and be President, and I wouldn't be able to steal this ship, which must be the important thing.
"But this former self of mine killed himself off, didn't he, by changing my brain? OK, that was his choice. This new me has its own choices to make, and by a strange coincidence those choices involve not knowing and not caring about this big number, whatever it is. That's what he wanted, that's what he got.
"Except this old self of mine tried to leave himself in control, leaving orders for me in the bit of my brain he locked off. Well, I don't want to know, and I don't want to hear them. That's my choice. I'm not going to be anybody's puppet, particularly not my own."
Zaphod banged the console in fury, oblivious to the dumbfolded looks he was attracting.
"The old me is dead!" he raved, "Killed himself! The dead shouldn't hang about trying to interfere with the living!"
Uploads aren’t even the biggest worry. If it turned out to be possible to upload analyse and upload personalities, it would also become possible to synthesize new personalities on demand to a required spec.
How much value does organic personality actually have?
Until the "dead" uploads outnumber the living, at which point they vote in a bloc to expropriate and enslave the meat-humans, as in the novel The Uploaded.
A. thanks for the suggestion, great, terrific, wonderful (was flux good?) but B. The dead shouldn't hang about trying to interfere with the living!