Couldn't all the author's and editor's draft happen in the central
repository as well? Git has branches, so it is easy to have an
author's branch. As everything will just have one history, it will
make things easier for reviewers and testers.
In github, it is easy to see other repos, as well. Just click on "insights" and then click on "network" or something like that, it shows every fork, every branch in every fork. in a nice graphical diagram. I'd quote the URL except that github seems to be "500 server error" just right now.
--linas