There is no discussion on Unity 7 and related matters in Ubuntu Forums Development section now. Every time Unity 7 is mentioned, the thread or the post is moved to chat and other places or the post is taken off and moved somewhere less significant. I’m not posting anything on Unity7 on 18.04 there.
Now that’s out of the way, if you and the group want Unity 7 to become an official flavour, the group has to create an Uubuntu iso and maintain that iso somewhere, most probably in sourceforge or ibiblio.org or nluug.org or some other place easily available for users, and where a download counter is. Also, the group has to have a separate website on Uubuntu. The Uubuntu has to have its own branding at the beginning. If that Uubuntu (or any other name) is a success, then the group can ask it to be brought in as an Ubuntu flavour. The Gnome, Mate or Budgie flavours etc, started that way.
The checking of Unity7 alongside Gnome-shell is completely another mater and is NOT going to bring any value to an Unity7 only distro, the future Ubuntu flavour. If the group is going to do work on making Unity7 (Uubuntu) an oficial flavour, the group has to concentrate ONLY on Unity7 on 18.04. Whether Gnome-shell would work well in 18.04 is someone else’s problem.