Please be aware that this was posted as a discussion, not a question (I always look at open questions only and stumbled upon this by accident).
We use a generic 'one time' customer in some quotations that get replaced with the "real" customer when sales order is created. To achieve that in the copy control from quotation to order the standard copy routine (002) needs to be replaced with a custom one (9... number):
For the custom routine (ABAP required) just copy the standard one (002) and comment out the piece that checks if the partners are the same.