Steam has had a dedicated feature for this for a decade now. Except it didn't do it over the network, just files which you had to provide transport for yourself
This is different than the backup feature, behaves extremely differently. The backup feature is so insanely slow that restoring from a typical USB media a 120GB game takes longer than downloading that same game on 100mbps internet connection.
This method I'm referring to (and probably what they will codify) is much, much faster.
