The idea seems very cool, but I wonder if there is anything like this that could have more language specific stuff like "in JS (or Ruby, or ...) format your hashes/object literals/arrays/constants/... like so."

I like this, but the list of supported properties seems pretty short. I can see there might be some difficulties making it language-aware since the file formats are simple globs, but maybe you could say something like:

  [*.js]
  language_style = javascript

and somewhere describe that language_style in more detail.