I think there should be a slight modification to Viewer and Viewer + license permissions where a user with one of these two license types assigned to them should be able to close out a CTA which has been assigned to them.
Our specific use case: CSMs run a series of playbooks and success plans which include CTAs for members of the sales team. All sales people have Viewer licenses. If one of these CTAs is assigned to a ‘viewer’ for action - they should be able to close that CTA (and just this CTA assigned to them) if their action is complete.