>>44050718I've played with this concept before. Found it would be better as an out of battle augmentation instead of a held item which could either get knocked off and render you useless or be yet another Knock Off sponge item. It's great because they can still hold another more useful item. You could apply the augment in many ways: tattoo, piercing, or my favorite a ball seal (to give those some practical use beyond just contests)
To keep things fair, the stat inversion would be indicated in team preview via some symbol. Because nobody should have to predict, say, physical Alakazam.