Is that at all possible on the time scales we're talking about? It depends so much on the distribution networks, health services, willingness of population and everything else of each individual country.

Unless I read this wrong. You are seriously suggesting that we should do global risk-factor prioritization? Meaning that the 50year olds in New York are not allowed to take their doses until 70 year old anti-vaxxerss in the Slovenian alps have had theirs?