This sounds more like a 'keep files in sync wherever the changes are made' solution rather than a 'I want changes made only in the canonical location and distributed (non-automatically) to the subordinate locations at times of my choosing' solution. However, I'll look into it to see if it might be useful.
I think I wasn't being clear; I don't WANT to use tramp. If I am cd'ed into a particular source directory in the rlogin session on a remote host, I want c-x c-f to edit the source file in the corresponding directory in the master sandbox on the shared filesystem, not the local copy on that remote host. If I did that via tramp it would be horribly inefficient, going through the remote host to open a file that is also directly accessible to the emacs via a more direct route. Moreover, if I were to edit the same canonical file via tramp from two remote host rlogin buffers, I'd have two emacs buffers with the same file when I want just one, i.e. they would differ in hostname but in actuality would represent the same shared file.
Rlogin.el gives me exactly the two capabilities I want, executing remote commands and relative directory tracking without adding others that I don't want, e.g. a remote shell's interpreting pathnames as if they existed on the remote host.