{Solved Thanks}
Would there be any interest? header tags are used to make table of contents, anchor tags create Index entries, all the formatting tags (tables, un-numbered and numbered lists etc) do basic print formatting. All the bold/underline/italic also render to paper. Sort of like a poor man’s TeX.
Has anyone done this?
Yes this is a thing and it’s been around for quite some time. If you’re trying to approximate TeX, you may also be interested in MathML.
I need to go lay down; I’m having flashbacks to the good old days of “XML everywhere for everything all the time”.