Can you give "save as" the ability to save "as a template" so that you can't overwrite an existing document. Indesign has this, and is very useful for protecting original documents that must never be changed.
ie. You open a template doc, and the only option you have when you save is "save as", therefore keeping the original intact.
This is great for setting up documents for my team as XD is the choice software for web / presentation projects now.