What if...he replaced Joe with Hillary, then won the election and subsequently stepped down to become Secretary General of the UN? Hillary becomes President and makes good with her promises to Obama now being negotiated.
A person from one of the Security Council's permanent members (US, UK, France, Russia, China) cannot serve as Secretary-General.
If that is Zero's dream, he's outtaluck.
The stricture is not in the UN Charter but is an agreed-upon article of faith in the UN.