The name of the vip file shouldn't be an identifier that VIPM uses.

Use some kind of GUID in the package that is the unique identifier between packages, and not the filename. I've had to change the filename of some packages a few times over the last few years (eg: changed product name due to a customer clarification), and it's a pain - now I have two (or more) parallel products that have schismed from the original, all because the filename changed.