I'm writing a small JavaScript engine that converts websites to JSON, and displays JSON as websites. Since an entire site is described in the same JSON file, the whole site is a single download, and it rebuilds pages in the browser instead of calling the server - much faster, especially on mobile.

If the browser had this small engine, it could render these sites natively.

Neat. But my comment is about the exact opposite: having a standard way to represent data in place of HTML and custom formats.

Your project sounds very interesting, is it hosted somewhere?

The site is in alpha, at https://www.sparational.com. it has links to my GitHub, and to the site engine on S3. It started as a simple Node project to host a blog and a few random pages. Now, the goal is a single-page application, in more than one sense.