Avoidance of RMA's

Does anyone have any ideas on how we can change our order management process so that after the order is in a closed status we could still go back and change certain pieces of information - such as po#/price and recreate an invoice without creating a different transaction type?? (Some of these changes include DFF changes)

Our users find the RMA process very frustrating when they have changes that doesn't affect inventory, only changes that should have been set up correctly to flow to the invoice.

I am curious how other businesses have gotten around the whole workflow process.