Copying POVs between reports in a book

Summary:

I have several different reports that have the same structures but different selections of metrics. Say, one report has financial metrics (e.g. revenue, expenses), the other has percentage KPIs, the third has statistical (headcount-related). I am using a building block concept, where users will be able to decide which of these reports to use, and in which order (that's why I'm not creating one report with three lines for different types of metrics.

The reports are designed to have Products and Entities in the POV. The idea is to have these reports collected into a book, define these POVs in the book, and then run the book. It is assume that all reports in the book will run for the same Product and Entity POVs. The question is, how do I optimize the member selection process for these POVs?