Off-topic, but not sure if you need to cryptographically secure your BTC from someone you want to inherit it to. Like, this whole mechanism (over e.g. leaving behind an instruction on how to just get access to your wallet(s)) is to make sure they don't try to steal your coins before you die. Not sure I'd want to inherit my holdings to a person that I feel could try stealing my possessions.
Fair enough. However, even if someone fully trusts heirs, there is still a risk of compromise Heir's private key and inheritance info so an attacker can steal money. Yes, this approach still does not guarantee that 100% but at least makes it much harder for the attacker IMHO.
If it's someone I don't completely trust, I'd be even more worried knowing they get my money
! That's an "accident" waiting to happen.