I was just talking to my colleague the super shadowy sponsor guy who is helping Indra happen, and he told me that the Chia blockchain just added a new feature to their wallet that makes a default time delay transaction that can be revoked.
If all transactions by default in wallets, unless the power user mode is enabled, were set to not be spendable for like 6 blocks, but also be able to then reverse the transaction between the block the spend appears and the deadline from when it can be spent, it would save a lot of people grief when they realise they sent it to the wrong address or that they were being scammed, if they realise it within 20-120 minutes they can reverse it. No custody required, just scripts.
After thinking about it, it seems like one of those things that should have been done from the beginning.
So obvious!
That plus full support for Child Pays For Parent (or is it child pays parent fees?) and RBF work until the tx gets in a block, this feature would let it be reversed for a time and then after that spent.
For on chain payments, this would be such a great safety feature. I'm pretty sure that it's simple to implement it already in bitcoin script.