Reassign purchase order via web service (REST/SOAP)

Summary: What capabilities (if any) existing around reassigning a purchase order to a different buyer via REST/SOAP?

Content (required):

We are trying to determine if there is a mechanism available via REST/SOAP to allow for reassignment of purchase orders to a different buyer whereby we can have some control around relationships between buyers. For instance if there are six buyers across an enterprise configured with one Purchasing BU, we may want buyer #1, #2, #3 to be able to view/edit each other's purchase orders, #4, #5, #6 to view/edit each other's, but not have access to view/edit PO's for 1-3. The six buyers mentioned for an example purpose would really be more like several hundred buyers