One easy, though incomplete, fix could be for interested users to keep local copies of their old list files, with dates added to the file names, then pull them in to GitHub as needed.
I have kept, more or less accidentally, some such "back issues", which I have found useful to help me reconstruct my travels on new/in-dev route systems. CHM, for those of us on that system when it went dormant, also provides a single snapshot of our past travels, though without systems later added to TM.