How to determine priorities?

What would have to happen in ERP systems to allow planners and buyers much better information? It started with a question from a material planner employed by one of the many manufacturing companies I have worked with and it got me thinking. This material planner was also responsible for procurement of the materials he planned within that company:

“After running MRP, how can I see in the ERP system which Purchase Orders, that have already been created in the system, are actually no longer needed because the need for the items, materials and components, noted in the Purchase Order line, has disappeared and these items, materials and components within the current set of production orders and Customer Orders are now NO longer required and are therefore no longer needed according to MRP?”

For a buyer, having hundreds of Purchase Orders running in the system at the same time, and where those Purchase Orders must match the demand for end products from Customer Orders as closely as possible, it is a fairly obvious question. The material planner/purchaser in question needed detailed exception reporting on this point because he simply did not have time to review all MRP results related to all Purchase Orders. However, with the results from standard MRP with only Planned orders that do not highlight the Purchase Orders or work orders that are no longer needed, that question is impossible to answer, while for a production company, that is not an illogical question to ask, both from the perspective of flow of goods as well as cost control.