That works pretty good with markdown files hosted on github pages as I don't have to move out of the CLI when pushing them online.
However, the use case that this workflow doesn't cover is when I write something that I'd like to send for a proofread to a friend of mine, who's an editor. He really loves his Word files.
As I'm a noob, I asked then ChatGPT to help me with a bash script that converts that .md file into a .doc file using pandoc. That worked pretty well.
My thought was if it couldn't be possible to use something like pandoc for converting an .md file into a templated doc with headers, footers, page numbering, even toc?
That wouldn't solve 100% of the use cases, but still could be pretty good.
And Markdown, well, its great in that it is simple, but I tend to hit its limitations very quickly for more complex setups - plain markdown won't do anything but the most simple tables, and of course, there is no way to define styles.
I would suggest that your use case is probably better suited for something like LaTeX (or Tex, for more direct control), og ngroff/troff if you want speed. Maybe Typist for a more modern take?
I'm trying to think of the use case where Markdown in VIM is not enough, but LibreOffice is too much. For what it's worth Bash is my file manager and I practically live in the CLI. I do write some technical documentation to go with my code, in Markdown. I recently wrote a long report in LibreOffice for a medical malpractice suite - I made extensive use of headings, paragraphs, quotes, tables, and bold text. My work templates have page headers and footers with page numbering, sparse embedded graphics, tables, a table of contents, and sometimes code snippets with syntax highlighting.
Additionally, all my document types use RTL text, which WordGrinder does not support. So I am more interested in the general feasibility of such an app, than in actually trying to replace LibreOffice with WordGrinder (at least until RTL support is added).