Back-to-Back Order Generation to permit Supplier selection

Sales Order Processing, entered sales items with fulfilment method of Supplier via Stock. When closing the sales order entry using the Save & Generate PO option, and where a sales item has multiple suppliers (i.e. not a single default) then it would be really useful to be able to choose which supplier to generate the PO against. For example, a sales order line for Consultancy Services could link to and permit back-to-back purchase orders on the full range of external consultants.