A project that you might be interested in that works *somewhat* along the lines of your post is the gemini protocol (geminiprotocol.net). its pretty limited by design, so maybe doesn't fit the requirements. i love this line of thinking though and gemini is, at least, a decent example of a concrete attempt in this direction.

one note about gemini is that its standardized a text format called gemtext that is somewhat analogous to gopher index files. there's no reason why clients couldn't serve markdown though. i believe some clients have first class support for markdown documents too!

i also wanted to say. i lost my old password account, but i've been following your blog for years and years. thanks for being an inspiration to a younger version of myself to get into web and especially thinking deeply about the intersections of web, design, and usability!