You can already do this to an extent with Bitcoin. After having a couple of friends be cavalier with the samples I gave them, when I gifted my brother some, I gave him a paper wallet to which I retained a copy of the private key. If he is interested enough to transfer the coins out of it, he can. If he loses it, I can restore it for him. This is not good for real-world usage, of course but you either lock in the transfer or you don't in my eyes (ignoring multi-key stuff for a second).
I have done the same. I hold the keys to all gifts I have given to family members.
And this shows where things like single mint e-cash schemes could be used.
Trust is NOT a bad thing. Being FORCED to trust is very bad. Especially being forced to trust vipers. But a family, for example, is a place where trust can thrive. At least a mostly good family... I know not all are. In this case uncle Richy the geek can run a mint/lightning node/whatever. He is the families "Central Bank" and can think up ways to offer ease of use, backups, instructions, vaults, mints, nodes, whatever... at the cost of trust. But uncle Richy is a good guy... and can be trusted by the family... so...