Declare it to be sovereign soil to both countries. Nobody pays taxes but the proceeds from exploiting its resources are split evenly between both countries after territorial costs are paid, its residents do not have representation in our Congress (Denmark can do whatever it wants), but can vote in elections like other territories.
If we want to build a base there, we can. So can Denmark. Each country is free to spend more than their allotment, and the two countries can decide on whose bureaucracies (like TSA or FAA) can better serve the land.
-PJ
That’s a lot of words to still be buying a country, which doesn’t happen anymore.