If you're going to go to that much trouble, you might as well just compile Emacs to Javascript with enscripten and run it natively in the browser. The download time might be painful, but then we'd have a web editor actually worth using.
You might not even need to implement all of emacs, just emacsclient and have the emacs daemon running on the server.
But why does everything need to run in the browser? You have a perfectly good OS and you can run Emacs natively and use tramp to open remote files over ssh. I do it every day, it's awesome because I'm using my local emacs configured the way I like it and I can edit files on any server that has sshd running. Problem solved.
It'd be nifty if I could have the power of Emacs available to me on a tablet. Since I don't imagine anyone's going to port it soon, being able to use it in a browser seems like the only way that's going to happen.
It's even 24.1. I only have patchy wifi now so I haven't been able to finish the install yet on my tablet but it installed and ran M-x tetris just fine on my phone.
There's more value in having Emacs cloud hosted, I think. The old joke that it's an OS masquerading as a text editor is actually somewhat true. Hosted in the cloud, you have really great bandwidth to other cloud environments, all accessible through low-bandwidth requirement TTY.
