I probably don’t need to tell you this, but that’s REALLY ambitious, mostly because creative authors do things you would never expect in a million years, and then they blame you when their docs don’t convert. Also because Word is Word.
What’s the technical plan? Where’s the repo? Are you building on pandoc?
I’m happy to advise on this; my first cut at the problem was over 20 years ago; these days I maintain the (RST, TeX, TXT, HTML) -> (EPUB, MOBI, PDF) toolchain that converts the 60,000 ebooks at Project Gutenberg (Blocked in Germany!).