But I guess this is an example of if you send to the wrong account that may not have a "buyer". Like what just happened to someone. The ability to cancel the transaction so your funds don't get lost in a random account.
I would keep such a feature out of the core. A user-friendly client may implement something like that entirely in the client - after clicking on send, the transaction goes into a list of "ready to send" transactions, and the user has to click on a second "confirm" button after double checking everything again. And the client may show a warning if the receiving account is not in personal address book, etc.