Do you have any idea how difficult it is to rank an entire coaching staff? It’s no easy task. There are no stats out there to rank the coaches, only the players themselves. And since there are no stats, there is also absolutely no way to compare a team’s coaching staff to the coaching staff of any other team, let alone something like a league average coaching staff.
I suppose the only way to do rank a coaching staff is individually. To rank the Detroit Tigers’ coaches in 2016, I looked at various statistics for the group players assigned to the coaches: the pitchers for the pitching coach, the hitters for the hitting coach, etc.