What if blockers did not allow any js loaded form any cname except the currently loaded one? This would surely break a lot of website that load their js from so

What if blockers did not allow any js loaded form any cname except the currently loaded one? This would surely break a lot of website that load their js from something like static.example.com but at least would help against server side tracking, perhaps it could be an optional feature that is off by default. Setting up a proxy for the same cname as the current page is loaded on is several times more difficult so I think Google wouldn't consider that as an alternative anytime soon.