I know of a patch currently under development (very near done, must be translated to English) for this exact function. Coder calls it "/etc/skel functionality for vpopmail".
If anyone else knows of another patch/method, please post.
I will post a link to the patch when it's complete. Also, I understand it will be submitted to Inter7 for their review...
Any news on this patch?
R. -- http://robinbowes.com