Is it possible to create a report for Accounts with a NULL value for Success Plan in CTA Group object?

We're looking to create a report to identify all accounts without a success plan created, active or draft. It appears the CTA Group object only pulls in records where these values exists - not allowing us to identify accounts we are missing information for.

I came across a very helpful article for building a boolean attribute within salesforce and create a rule to populate this from Gainsight (link below). That is my go-to option right now. Does anyone have experience with another workaround that delivers these results in the Gainsight platform and not requiring data loads between SFDC and GS? 

https://support.gainsight.com/Product_Documentation/Rules_Engine/Examples_and_Tutorials/Tutorial_Ide...