Change agreement on purchase order

Summary:

I have read BUG 22955739 : UNABLE TO ADD CPA TO AN APPROVED PO. What I now found is that I can use a sandbox to make the agreement field editable in stead of 'read only'. What are the implications of allowing this?

Content (please ensure you mask any confidential information):

Once a PO is created it can be that the PO is not referencing a CPA when it should, or not referencing the correct CPA. In stead of duplicating the line to add the CPA, it would be great if this can be edited in the UI directly through a change order.