How about a state that offers citizenship but not residence.
Imagine a globalized city, with actual physical resources, an economy, citizens, institutions, and cultures already in place. Now suppose that the citizens of that soverign city extended citizenship to every person on this planet, sharing all rights, laws and economies they enjoy with all. Every child, from central Wyoming to Tokyo, would guaranteed access to the laws and economy of this city. In the city, they would have to right to a fair trial. No matter where they lived, they would be guaranteed the right to participate in the markets of that city. What would not be guaranteed, however, would be the right to physically occupy space in the city. Though the freedoms offered could be described as non-corporal, their implications (access to a fair and balanced legal system, access to globe spanning markets and access to the entire world’s culture) could safeguard, elevate, and set free the souls of all people.
There are complications and downsides. This will be for next time, naturally.