S-expression schematics. Nice. There are entire markup disciplines that probably should have just been s-expressions and saved a few billion people hours.
I have a bit of mixed feelings here:. If it was JSON or XML, you could use existing tooling to work with the format. Say, using jq to extract metadata from a full folder of kicad files or generate files or components from a shell script.
Sexp's are a step forward, but they are still only half of a standard. Charsets and escaping rules need to be defined, etc..
https://en.wikipedia.org/wiki/EDIF
At least for netlists, it is a popular format.