The current solution to enable customer to start from an existing drawing doesn't work.
Instead, I propose a new solution. When a new diagram is created, we should instead give the customer the option to start from a previous diagram as a template. They can then select from a list of existing diagrams in a doc mgr like interface. Once they find the diagram they would like to start from, we simply copy this diagram data to the current one.
You are talking here about creating a new diagram, starting from an existing one. From a user point, what I want to do is. I'm looking at my current diagram and want to copy it onto a new page. I guess I just want to point out, that you might want to support this kind of "workflow" also by providing a "copy to other page" option from the current diagram.