Most JS programmers seems to use modules (require/import) as masqueraded globals, like importing complexed functions instead of just standalone modules. And in that case it's better to just declare all dependencies in the root (html file). You would probably want to use a package manager though, to keep track of name conflicts and manage the script tags (dependencies of dependencies).

As for central hosting of packages I think it will work. But we will probably need to be able to have many src attributes in script-tags for redundancy and optimal caching.