That's a vector for literally all assets so adding a random delay to every layer up to the last Paint() is the only real counter.

It can be mitigated by adding a property to scripts to allow/default/deny shared domain resource caching, and the ecosystem can benefit from jquery/etc from being hot but still maintain opt-in default/backwards-compat status.

that, combined with the already established HTML <script> integrity Attribute and you are gravy