Perhaps one can use the adapted version by using GreaseMonkey. I'm using GNU LibreJS to block all non-free JS from YouTube and also I'm using GreaseMonkey with an YouTube video player for which I forgot the name now, and it works as expected.
One other alternative, that needs to be implemented by the site developer, is to make a site not load any JavaScript, and instead, ask the users to download a GreaseMonkey script instead. Perhaps this would allow the users to keep different versions or even revert versions of said script (since GreaseMonkey seems to have a package manager of its own, although the process is manual, since you have to visit the @updateURL, from there get the desired older version, and revert the installed version by installing the older one and disabling automatic updates only of said script).
