You can add an arbitrary value instead of a PHID as a repo when adding a path to a package.
This leaves you with some lovely Unknown Object (????)'s
This probably has some un-intended side-effects elsewhere also...
In addition to this, if you have no repos and you try to save, we throw pretty exceptions :) (we should probably not allow users to try and save if there are no repos)
(e.g. /owners/paths/1/)