Best Practice to Adjust Project Information in Matched Supplier Invoices

Hi,

I have the following situation with a customer.

- iProcurement, Purchasing, Payables and Oracle Projects are installed and used

- Customer doesn't want to enter project information at requisition level because requisitioners are have not the knowledge to select the correct project information for each requisition

- There is a cusomisation to generate the Purchase Order automatically from the Requisition so is not possible to update project information at purchase order level

- Customer wants that AP enter the project information at invoice level but the problem I have is that the matched lines with the PO are not editable (they are greyed out)