This is an interesting project, to formalize the INI format to express more complex data structures.
I’m not inclined to want more complex data. I know, people have used XML and JSON to specify configuration, but, I just dislike that. I’ve used YAML, and though that was good for a few years, but lately, I’m back at INI.
The problem with expressive configuration languages is that you end up with tools like Ansible (which I like) where, instead of defining a little language, or being used as a Python library, the entire “programming language” is in YAML.
Rant over. I will probably use TOML next time I want to use an INI file 🙂