I think Zava was the clearly necessary character in terms of plot progression - he allowed Richmond to have a period of true suckiness but still be in a position to realistically come back and win once they figured out what was wrong.
Unfortunately Barbara, Jack and Shandy were all as you said necessary for Keeley, but only because they could not figure out how to connect Keeley to the main plot anymore and needed to give her something to do. Zava at least drove both the main plot (in terms of positioning Richmond on the table) and character development (mostly Jamie, but also I think he progressed all of the coaching staff because they took the “easy strategy” at first and then after he was gone they had to figure out how to actually strategise… something they had in the past just outsourced to Nate/Zava’s easy scoring).
I wish Keeley had been more connected to the main plot and characters… she could have stayed on as team PR for another year (realistic given her level of professional experience) and still had plots with the team…
Just when I had money to burn :( I hope you can still get the version Richmond is in…