Currently scorecards cannot be applied to features from the Product Line level down. If the scorecard selection were part of the Feature layout, then you could apply a custom layout with the corresponding Score field and it would inherit from the parent line down. Another option would be allowing a bulk update from workspace settings, specifically feature scorecard. Currently I have created a report to see all of the products under a particular parent line, but must manually go one by one to update the scorecard for features under that product.