SPM using local repository mirror

Just wondering... When developing packages whose dependencies are large in size or quantity, or where there are nested dependencies, what would be the work-flow (or Package.swift updates) to allow retrieving dependencies from local storage (or internal server)?
Using github.com based repositories could lead to a rather large load on both github and local network if developers are cleaning/building often.
This issue is further compounded by the fact that revision tags need to be jigged to give the right results considering the Package dependency requirements in the graph. Seems like working with a local mirror is what you might call your worst nightmare.