"Is this a thought experiment or do you actually want to build something that solves the problem?" - yes to both 

True. If they don't get the idea after you say "you shouldn't hold your bitcoin with us or any other custodian" and provide you with a coinbase wallet address maybe they just aren't going to get it. 

Is this a thought experiment or do you actually want to build something that solves the problem?

grayruby

Yea.....and they send from one custodial walelt to another cos it allows onchain....or to Conbase acc....

designsats

bitcoin

Brainstorm time - how to help normies with self-custody? (5k bounty)

I think the best you can do is force them to provide a btc address and then prompt them when the balance reaches a certain threshold and fees are at a reasonable rate. 