Why not just make more good moves of the other attack type? Aside from outliers like Psychic, Fighting (and even then there's still some Special ones), and Fairy, there's really no flavor reason most types shouldn't have a mixed physical/special pool. In fact, as
>>55972391 pointed out, several moves are balanced on the idea that their use decreases the stat they calculate off of, so there's actual negative impacts on balance when considering those moves. Even if you go out of your way to make the stat drops opposite (which GF will inevitably fuck up somehow) it would really only be useful in a pre-split game, and since we live post-split where almost all romhacks implement that system as well there's not a particularly good reason to do it.
