Sorry for the late response.
Did you just submitted this through our ticket system?
I will post our reply here just in case.
Per your description, it seems like managing this through “Team Delegation” (Team packages) could work better for you instead of using a policy.
You can create (or make one of the existing packages) a principal package of PRO & RC. When you need to release RC you modify the parent package and apply all changes, then when promoting you can specify to not promote and build secondary packages.
The flow that you describe is exactly what team delegation can help you with. Check this link for more information and let me know what you think.
https://www.genuitec.com/products/sdc/learning-center/delegation/managing-principal-packages/
https://www.genuitec.com/products/sdc/learning-center/delegation/managing-secondary-packages/
I hope this helps. Let me know 🙂
Anabella