Is there a way to populate a single Requested Delivery Date on a PO header?

Summary: Our client has Purchase Orders with large number of lines (50-100 or more). They have a same Requested Delivery Date for all the lines on a PO. But now they have to add it at each line. It's very troublesome and their suppliers get confused with all these dates. Thus, they wish there should be a single Requested Delivery Date on PO header. Currently Oracle doesn't have such a functionality. But is there any way to get it on the header?

Content (required): We want to have a single Requested Delivery Date at PO header because our client has PO's with large number of lines on PO with same Requested Delivery Date. We had raised an SR for this, but they replied that there's no such functionality available as of now.