Potion Effects based upon Item subtype/damage

I'm trying to come up with ideas for a mod I'm making.  One idea was to add a new potion ingredient set for an item, but I've run into a snag.  The item in question has subtypes, and I do not wish to have all subtypes be usable as a potion ingredient, or even the same kind.  The potion functions available do not take this into account.

My suggestion is to add a set of functions that uses the itemstack's damage value to determine the potion effects/ingredient status.  The base versions in Item could reference the original functions which ignore this information, and derived items can just override them.