I’d pay to have delete actually delete email completely (not just from my inbox, but from all as well).
I think certain enterprise-y email solutions have this, but there's no way to have that happen in the distributed email ecosystem unless all your messages were just links to a website that could delete the content centrally, or similarly, jpg's of rendered text that were somehow forced to be remotely fetched each time.
I know I had a former boss that loved to try using the outlook "unsend the stupid thing i sent" feature.
Little did he know the cients could turn that bit of functionality off. He hated when we replied to the emails he had "purged".
other than that, i don't think receivers like the idea that others can control what's in their inbox.