Bugs v. Psychics
Also, for a completely superfluous and complicated new feature, I think it would be neat if they made more of an effort to make each Pokemon feel more like an individual. Really give you a sense that "this is MY Pokemon." I was thinking they could maybe have nature effect animations in some way. Maybe subtle, or maybe each one has its own idle animation, dunno. Then, the IV's could effect its model and texture. For example, something with high HP IV's may appear physically larger? Since it's kind of silly to believe each and every Pokemon is the same height (even though I would love if that were true for my own reasons). IV's could effect the palette of its textures (even if that would mess with some shinies), or cause different patterns. Different parts of the models could be effected, maybe bigger cheeks on a Pikachu or longer horns on a Charizard.
Could wrap up any inconsistencies like that too lol. "Oh, the six fingered Electabuzz from Stadium was just a different allele type." Anyway, just a little something so that even though all Pokemon are basically the same, there'd be little things that maybe only you as its trainer would notice and know that it is yours.
Imagine an Onix with like veins of different ores peeking out from its boulders... so much you could do.