Hello Wayne, if you have the EPDM addin for SolidWorks enabled, there are a couple of options in there.
The second option "Automatically name files on save as with serial number" could be what you are looking for. So designers can work with files in and out of the vault and give them descriptive names. When they are ready, then can open them, click File, Save As, and the file will be renamed according to your serial number convention.
I hope this helps.
We ran into the same situation with our vault. We ended up "disabling" automatic file naming with a serial number. We added a button on the file data card to allow the user to assign the serial number when he is ready. This required an Add-in but wasn't too difficult.
Just set up another set of templates for parts and assemblies. Make the data card available to name the parts whatever they want when creating the file. Then when they are ready to assign SNs, just copy tree. We have this as an option through our vault.