This is really interesting! I've hoped of a scenegraph based web in the past, all rendered in a canvas (indexing can be done by serving a simplified html representation by checking the user agent). I think the most challenging part is text rendering, but some people have done some work in this area (https://github.com/astiopin/webgl_fonts). Also, we may need some sort of API to trigger keyboard showing on mobile device. Anyway, congratulations!