A browser plugin to make (Google) fonts offline

I am concerned about my privacy on the internet and i think using cdn's for data that is very common and often reused - such as fonts - opens a huge door to user tracking.

In a short research i did not find a browser plugin to replace online font cdn's with locally cached fonts. I wanted to open a discussion about the feasability, problems, ideas and interest in such a plugin.

If you think this is a good idea and you'd love to work on it, you are very welcome to "steal" it. I will hardly be able to work on it myself in the near future.