Hah! That's also how I first learned about the zip trick with pptx.
Had never considered it generalizes outside of OOXML files. I'll give it a try next time I'm poking around another file format
JAR/WAR, iOS apps, and others
In fact, relevantly to this article: https://sqlite.org/affcase1.html
Zip is a known format, so library support is mature. It can contain a local file system. And no one is going to casually muck about in it, so you can trust the structure.