Requisition Vendor Email

Has anyone ever implemented any functionality (whether custom or delivered) to allow Buyers/Requesters to add vendor email addresses at the requisition line level?

I realize the vendor email addresses pull into the PO, and can be overridden on the PO by the Buyers. In this case, the Buyers would like control of the vendor email address at the requisition level. Email addresses change frequently and relying on a formal update at the Vendor level is cumbersome and doesn't fit the business process.

Thank you

PJ