1. Memorize your seed.
2. Prove you have the seed by signing something a message just before death and giving them the xpub
3. Tell them if they succeed they can have the balance
4. Enjoy trust-minimized cryogenic preservation
Discussion
1 BTC should be at least 1% of its maximum theoretical value (32T 2023 dollars) in a few hundred years - so like a few hundred million 2023 dollars.
I wouldn't trust them to not just decode the neurons with the seed phrase on that long of a timeframe.
"Why do we need to thaw him when we can just read his brain state now?"
True. Though, the article relies surprisingly (to me) heavily on them manually recreating your brain structure. If that’s the way it turns out, it’s not all bad.
Knowing your brain structure is a prerequisite for both accessing the funds (knowing structure + decoding structure) and for reconstructing you (knowing structure + actually rebuilding structure). It’s not a total loss to be able to for sure give them a huge bounty in figuring out how to map the structure. They may find it easier to map then recreate then ask than map then decode. Kinda doubt that though.
The worst would be them being able to map and decode but not reconstruct any time soon. That could be a huge motivation to saw you apart and not reconstruct you.