Workspace reporting - add in information from child records

We maintain a large number of products and our CPO has mandated that all products have an initiative for a particular type of work. We use custom fields against initiatives to categorise our work and whilst we can apply a filter to identify which workspaces have such an initiative by applying a filter to the custom field, we can't identify any exceptions where these initiatives don't exist. This sort of exceptions reporting is vital to identify gaps in our roadmap