I've seen this idea proposed before, it is not new. Miguel de Icaza brought this up on his blog last May. The idea took hold in my head and I haven't been able to forget it since then. I think it's a great idea. No, not just great, genius.
Google is going down a similar route with NaCl, but I think they are missing the point there too.
Google needs to go one step forward on their idea, Dart is not enough to revolutionize the industry, but allowing developers to write in a language they are familiar with and good at, THAT would revolutionize the web.