I had a ton of fun using Kaitai to write an unpacking script for a video game's proprietary pack file format. Super cool project.
I did NOT have fun trying to use Kaitai to pack the files back together. Not sure if this has improved at all but a year or so ago you had to build dependencies yourself and the process was so cumbersome it ended up being easier to just write imperative code to do it myself.
Nice. This was one of the main shortcomings in Falcon that pushed me to switch some projects to FastAPI. That said FastAPI had many other benefits that went far beyond API specs.
https://github.com/chiefautism/privacy-parser