I had a realization a while back, that in my opinion LaTeX isnt really needed anymore. Pretty much anything you can do with LaTeX, you can do with HTML. Want a PDF? Most browsers will print to PDF now, or you can use a library like this:

https://github.com/dompdf/dompdf

Need a page break? Here you go:

https://developer.mozilla.org/Web/CSS/break-after

Im not sure what you would do about TikZ and stuff like this, but I have seen some pretty wild stuff in CSS, so surely its possible:

https://pattle.github.io/simpsons-in-css

In Pandoc, what you would do is you would use a general Latex plugin, and then TikZ supports PNG or SVG output by 'standalone' (https://tex.stackexchange.com/questions/51757/how-can-i-use-...), and you can either save that to a file & use as an image or you can inline them.

This uses Latex at compile-time, but considering the extent to which TikZ is a graphics DSL, I wonder how hard it would be to implement a TikZ->SVG compiler as a standalone tool in a different language? (Or make it available in a variant like Mathjax? Like https://github.com/kisonecat/tikzjax except without running an entire TeX engine in the user's browser.)