I think you're downplaying how much separation there currently is. You're mentioning top and bottom, for instance, which is already separated. The wrestling and BJJ moves are very different, even though some fighters have moves from both disciplines. And there are ground perks that further specify things. I'm not a fan of how they're arranged, but they help with differentiation.
What stands out in what you propose is differentiating between FG and HG. I'm ignorant about grappling, but I questio if this separation is really needed. Do yall really llok at some fighter and think in terms of this guy has a great HG, but not FG?