Wouldn't a better, but partial, solution be for browsers to preload the top x common libraries? All other libraries would probably have to follow this new rule.
What version(s) of those libraries? I mean, I don't deal with this anymore... but I've seen sites literally loading half a dozen different copies of jQuery in the past (still makes me cringe).
As soon as you add something to JS you have to support it forever. Its better to let sites pick what they need and scrap what they no longer need. JS has already added most of the useful stuff from jQuery. If browsers included a built in version of React it would pretty much lock in the design as it is now without room to remove and replace bad ideas.
https://decentraleyes.org/