Would auth object C_PRPS_VNR - PS: Project Manager Authorization for WBS elements apply?
"You can use this authorization object to control who has access to the WBS elements in the Project System depending on the person responsible for the project ("project manager")."
You would enter a number in the person responsible based on values in table TCJ04 (instead of SAP User Id)
Check out SUIM > Auth objects in class PS for Project Systems