If there are multiple packages then there will be multiple pin numbers. Would you have a different variant for each package?
I really don't like the idea of creating new variants. It's already a huge amount of work in multiple projects I'm involved in trying to support all the different ATmega1284P variants and some other chips also have multiple common variants now (Wiring vs MegaCore for example). It's really nice that the variants used on the official Arduino boards have become so standard.