What do you say about "unit" as a unit of measure, including or excluding from the nemeth switches?
While it doesn't fall under the categories you mentioned (US/international/metric systems), it seems just plain wrong not to consider "3.2 units" a math expression.
FG p5. 4. When words are part of a ... math expression, they are as much a part of the technical notation as are the letter variables, numbers, signs of operation, etc.
And this statement doesn't preclude other words being part of a math expression ... it sure would be helpful if the wording was more definitive! Do you know if BANA has any plans to expand/hone the current Guidance?
FG p7 5. Measurement units (e.g., feet, ft., min) adjacent to related numbers transcribed in Nemeth Code are part of the technical expression and are transcribed within the Nemeth switch indicators.
I'm sorry to keep nagging you with this issue ... it's a real bugaboo for me!