How big does the resulting binary get?
edit: oh, looked at the demo on https://tikzjax-demo.glitch.me/ and it seems like it is just a couple MB. Not bad.
You also won't have something nice like $$ or \[ \] and will have to put the
<script type="text/tikz">
\begin{tikzpicture}
...
\end{tikzpicture}
</script>
tags directly in your markdown, if that even works.