Call to Action: Include Overdue Task Count

I'm trying to create a report for our CS team managers that shows the count of CTAs that are either overdue or have tasks that are overdue. Essentially, I want a report grouped by CSM, that shows the 'Overdue' count that displays in Cockpit when CTAs/Tasks are grouped by Due Date.

As far as I know, ootb, I can only get this info through 2 reports...

1. Create a report on the Call to Action object that summarizes CTAs that are overdue. Cool, but what won't be included in the roll-up are CTAs that aren't yet due, but have associated CSTasks that are overdue because the CTA itself isn't overdue yet– fair enough.

2. Create a report from the pre-built Data Space, CTAs and Tasks. Include all tasks that are overdue and count distinc Call to Action IDs. This is ok, but again won't include everything I want. Missing this time will be CTAs that don't include playbooks/associated tasks.

Together, these two reports will provide what I need, but it's not as clean as it could be. What I really want is 1 report grouped by Assignee/CSM with a roll-up summary (count) of CTAs that are overdue or have overdue associated tasks. Which I think would be possible if there was a field on the Call to Action object that was a roll-up summary of Overdue Tasks. Then I could just create a report from the Call to Action object and include the report filters CTA = Overdue or Overdue Task Count > 0. Already included in the managed object are the fields:

• Task Count
• Open Task Count
• Closed Task Count

Thought I could just add a custom field to the object and populate via Rules Engine, but I kinda forgot that we can't write to Call to Action (outside of create or close CTAs)... womp, womp. Going to try to create a relationship roll-up summary via sfdc Process+Flow, but still think this field would be a solid addition to the managed object.