> Is anyone aware of a CMS (like MkDocs, Pico, etc.) that uses 
> pandoc-flavored Markdown? I'm using pandoc to make pdfs, but need some 
> things other platforms don't offer, like fenced html, or is it fenced 
> markdown ( :::boo creating a <div class="boo"> tag).
>
> I'm trying to avoid rolling my own, but I will if I have to I guess.

Have you considered [Hakyll](https://hackage.haskell.org/package/hakyll)?
It does require you to write some simple (well, depending on how complex
of a site you want of course) haskell code but provides a powerful
library to make defining static sites easier.