Making static content that is tied to work only if you have specific web server with specific plugin seems... counter-productive at the very least

> I've already added code to mod-include to detect and conditionally react to nested includes after dealing with a bug in its existing handling[1].

and even more if you need to patch the web server to even make it work.

That being said jekyll include syntax is quite rich https://jekyllrb.com/docs/includes/ so you'd probably just do fine with it and minimal legwork