The most reasonable international approach would be to label chords with Roman numerals with the type of chord as an (exponent) with arabic numbers.

For example, Roman numeral "I" with a maj7 would be I maj7.
In the key of C, "I" would be C, G7 would be V7, Eb would be bIII. C# would be #II.

Most musicians internationally use this type of nomenclature bypassing the need
for a fixed or movable "do" to express chords.