This is not a new idea: EDIF has been around for a long time:

https://en.wikipedia.org/wiki/EDIF

At least for netlists, it is a popular format.

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..