Don't get me wrong, but respectfully, this has *NOTHING* to do with SMTP.
SMTP is not involved and not changed.
Therin lies the flaw in your plan, as smtp must continually change in a
distributed fashion in order to effectively reduce the amount of
egregiously time-wasting email that flows through its veins.
No you are counting the chickens before the eggs. If you have no more eggs,
then you won't get any more chickens.
The misuse of SMTP has to be attacked at the root cause, which is my proposal
(go study all my posts for full logic), rather than morphing SMTP in a never
ending game of "cat and mouse".