How to allow receiving for a req BU without also allowing new requistions to be enter for that BU?

Summary:

Our employees are assigned a custom PO Requester role along with data access for their current Requisition BU (Req BU 1). The employee enters a requisition. Then the employee is transferred to a new LE/Requisition BU (Req BU 2). They retain the PO requester role and are assigned data access for their current ReqBU (Req BU 2). At this point, any new requisitions will be created under their new Req BU (Req BU 2), which is what we want, but they're no longer able to view or receive the requisitions created under their previous Req BU (Req BU 1). We've