Hi Wayne
There is a setting in SO >> Settings >> Order Settings called Credit Notes Update Invoiced Qty. What this does I believe is reduce the invoiced quantity on the sales order for you to then recreate the invoice.
So it is possible. However, this has to factor into the company's processes. The order does become invoiceable and will be invoiced again if the maintenance is run to invoice orders. In my experience they may simply want to credit the invoice and never re-invoice. In this case, they have to remember to close off the order after the credit is raised.
I think you have to have this ticked in the system to be able to reinvoice from the order after the credit note has been raised. Will work for you but none of my clients as they want the order untouched after the credit note is raised.
Sanjay (Syntec Solutions)