The implementation of the System loader in the polyfill, as I have understood it, is described here - https://gist.github.com/guybedford/3712492cf0f629eed761.

Basically, there is a distinction in both the normalize and locate functions between a URL and standard module name.

In the model browser loader, this distinction is implicit by the fact that non-relative names (not starting with ".") are just passed through the normalization function, and ToAbsoluteURL is run to convert the normalized name into an absolute URL relative to the baseURL, resulting in absolute URLs being left in-tact.

normalize would typically allow custom mapping (eg `jquery -> lib/jquery-1.9.1`), and locate would allow custom paths (eg `lib/jquery-1.9.1 -> https://some-cdn.com/lib/jquery-1.9.1.js`).

@arv so since URLs are exceptions to both functions I think what you are looking for is supported here anyway?