> DOM diff-ing on the server and have the thin client only transfer the changes. This would hopefully make the initial payload extremely small and the changes being transferred minimal as well.

To achieve similar results, you could granularly partition the build so that scripts are lazy loaded as needed. This would be like sending diffs, except only once since the client can reuse them.

Having a server manage the DOM state of every client, and maintaining sockets between them, seems like a complex apparatus.