unity-session (#it will pull ubuntu-session as well ?)
No . ubuntu-session came with gnome-shell or gdm3 so it has to be removed manually. We cannot have ubuntu-session in there because it will put login options (gnome-shell on xorg) in the.
I would like you to consider this idea:
If we use gnome-meta , remove gdm3, ubuntu-desktop, ubuntu-session , then, rename it and use that file for now else there could be breakage with depends. It has worked very well in cubic in #chroot. I am only mentioning this so as we do not have to create extra work for ourselves. We can always modify the meta includes and recommends as the development progresses.
Correct me if I am wrong but there has been a lot of changes during 17.10 cycle and unity-session is very dependent on gnome blocks so we want unity and gnome components working together harmoniously atm . If you think your current edit of the meta package you have created will suffice then we I can build an ISO and test it. But perhaps your suggest will eliminate a lot of work.