How about emacs in tramp mode? Or even mounting the remote file system with sshfs and using whatever editor you had installed locally?
Almost all of Theia's features are based in the backend.
The emacs equivalent would be like having emacs in daemon mode and a tcp based emacsclient locally. (I wish that existed)
Also the idea is to have something a bit more modern and appealing to the mass of javascript/web devs out there.
Theia is still far from replacing emacs, but as an emacs user myself and a Theia dev I hope I can bring what I love about emacs to Theia :)
The local socket opened is used only for configuration between emacs and emacsclient see: https://github.com/emacs-mirror/emacs/blob/master/lib-src/em...
So it seems possible with socat indeed, I'll have to give it a try :)
One problem that I see however is that emacsclient also forwards signals to emacs when the window changes size for example, I don't think that will work with socat