It would be useful in some cases to be able to have a local git remote that acts as a proxy to other remotes. That is not currently supported. See f98605bce7ecfa7fd155d501accb2734d3e9a422.

Supporting this could be as easy as using git-annex-shell on the path of the local git remote and speaking P2P protocol to it.

A possible complication with that: In between uses of a local git remote, git-annex is careful to flush files and close handles. That is to support removable drives, so nothing is lost if one is ejected while git-annex is running, and to make it possible to unmount them. If git-annex-shell has to be spun up once per file, and then shut down afterwards, that might be quite slow. Possible approaches to deal with that would be a) document that a local git remote that acts as a proxy will keep a removable drive in use as long as git-annex is running or b) avoid tearing down the git-annex-shell for a few seconds so it's still available for the next use.