I think the parchment paper is a little weird since while it properly conveys the idea that it is ancient, it is being spoken not read, it's also a little jarring. However I think if it actually is being read that you should keep doing that as it looks nice otherwise (such as many points during riko's initial interactions w/ moogie).
Regarding your question; more obviously, you could also make the main script appear in another font and then have the normal font and script appear above it, maybe 0.8x the size. It's simpler to do
and avoids the issues you alluded to with the above suggestion but is perhaps more boring than such.
Regardless of what you choose to do, if you do I suggest doing it with these fonts packaged in an .ass :
https://frozenpandaman.github.io/abyss/ 