There is another current discussion related to this: Different delivery notes - #5 by Frankie. The heart of the other thread concerns differences in what address, if any, shows on a delivery note depending on where it is copied from. The differences that now exist stem from the workflow imagined at the time delivery notes were first added to the program. Now they are being used for additional things.
It may be that all sales-related documents should have fields for billing and delivery addresses, possibly with checkboxes to tick when one is the same as the other. Delivery address might include a third-party name. That way, no matter what your work flow is, you can copy one form to another and have whatever information may be needed.
I suppose longer thought might convince me that all purchase-related documents need separate billing and delivery address, too. Everyone won’t use these, but some definitely will.