It's a very interesting idea. I don't think I'll use it and I think the downsides outweigh the benefits but it is still an interesting idea.
In all of these cases, the answer is not TOML, YAML or JSON — or FAMF for what it’s worth. It is goddamn database.
I was about to boo and hiss, but if you mean something like sqlite as an application file format I'm more tempted to agree.