Stephen,
Your group merge feature has been added to Fedora Rawhide.
Official rawhide build in progress:
http://koji.fedoraproject.org/koji/taskinfo?taskID=12536544
Even if it doesn't go into 2.23 I expect it will go into 2.24,
and because it doesn't add new ABI/API I plan to keep it in
Rawhide and include it in F24, even if it's not in upstream
yet.
Cheers,
Carlos.