This would be useful because it would save time when entering invoices and the vendor has made a change to their address or you notice an error in the current address. Currently the process to update the address is to either stop working on the invoice and go update the vendor's addresses and then restart the creating the invoice. Or to create the invoice, go add the address to the vendor, then edit the remit address on the invoice. If you are working through a lot of invoices the hassle of having to jump out of invoice creation to update addresses is tedious and time consuming.
This should work by having an edit button right next to the Remit to above the address dropdown. When you click the edit button it will bring up the Edit Address Popup Box.