Unifying national location identifier schemes under a single key presumes that a data consumer can straightforwardly determine the scheme geographically based on the containing administrative boundary. Are there any situations where this assumption would fail? For example, does any country maintain military facilities on foreign soil while assigning their own identifiers rather than using identifiers assigned by the host country?
I saw the suggestion for these language and script codes on the talk page, but does any national civil aviation authority actually assign location identifiers to a given facility in multiple writing systems or even multiple languages? Maybe that should just be limited to the unofficial refs, to the extent that any unofficial body assigns refs multilingually.