When there's no global clearing house for those identifiers, maybe namespaces would help?
Related: The editorialized HN title uses nanometers (nm) when they possibly mean nautical miles (nmi). What would a flight control system make of that?
Every aircraft I’ve ever flown as either Pilot in Command or required crewmember, and also every marine navigation system I have used in my life has displayed distance information as nm, Nm, or NM, interchangeably. I have never been confused by this, and I have never seen any other crew be confused. I have not ever seen any version of nmi used, in any variation of capitalization. This includes Boeing flight decks, Airbus flight decks, general aviation Garmin equipment, and a few MIL aircraft. And some boats.
The reason idents for radio navaids (VOR/NDB) are only three characters is because they are broadcast via morse code. They need to be copyable by pilots who are otherwise somewhat busy and not particularly proficient in Morse. For this purpose, they only need to be unique to that frequency within plausible radio range.
'nm' and 'NM' are the accepted abbreviations for nautical miles in the aviation industry, whether official or not.
Related: The editorialized HN title uses nanometers (nm) when they possibly mean nautical miles (nmi). What would a flight control system make of that?