That workitem describes how to have different repositorys at package level without having to configure/switch repos on your machine in order to update the packages, like this:
Elmah sourced from http://wellknownrepo.com/
HelperUtils sourced from \\privaterepo.
A necessity indeed!
What I am attempting to propose a solution for is when a package itself has a dependency, in the example above, for when HelperUtils has a dependency that is sourced from http://wellknownrepo.com/
Without the ability to 'source' your dependencies when you author a package, Anyone who manages a repo has to pull in the whole dependency tree into his/her repo!
When I'm authoring a package I want to specify exactly where my dependencies come from.
This is a different issue (repo-side) from workitem #20 (client side)..