Hey cool idea! I'll definitely consider that and variations on it. This could work for Pull-direction operations like fetch/pull, but maybe not as well for push since the remote would still be affected in some way.
Was gonna suggest the same! I use this countless of times. It's really cool how you can push/pull to a bunch of different things, including directories, ssh hosts, anything that can act as a directory (network mounted FUSE directories) and more.
Personally I use it a lot for backing up git repositories to a USB stick where I have a backup of every single repository + its branches and commits in case I ever need to recover from them. And I can keep my GitHub remotes clean without 100s of branches.
Will need to think about it more...