Thanks for your thoughtful reply, @harding.
There is a lot to respond to here, and I will do so in this thread for the most part, but I wanted to make specific note of your point on vaults:
Vaults can be done today with presigned transactions. The presigned versions are a lot harder to implement correctly than with
OP_CTV+OP_VAULT, they can’t receive payments without interaction with the payer, and the vault user needs to store more data. However, it seems to me that if there were high demand for the general ability to have hot spends announced onchain with a cancellation window, a significant number of people would be using presigned vaults—but I’m not aware of that happening.
Because this is a rich subject and, unsurprisingly, I’ve got a bit to say, I have spun out my response into a separate thread: