While creating a sales order you should be able to create a purchase order for a drop-shipment. There is a similar function for non-drop-shipments already via action pane, but we are looking for the same functionality regarding drop shipments. Customers do not want to leave the sales order and create a new separate purchase order... customers' current software already has this option where they can issue a P.O. from S.O. on the same screen (fishbowl).