If this is already in and I just missed something, feel free to correct me. If not, then here goes: a method of damaging enemies. This gives me several ideas:
-First of all, logical sense: why can spikes hurt me, but not them? For this, you could even just make it a new combo type(s): hurt enemies/hurt indiscriminate.
-New strategies involving bait. What, it's useful all of the sudden?
-Custom Boss potential: you know that one boss in every RPG where you can't beat him no matter what, except you're supposed to instead attack the other target that you discovered by accident by pressing left? And the "secret target" drops a rock on his head or something? Yeah, something like that.
-FFCs: allies. Someone that runs along with you and attacks enemies. You could REALLY make some interesting things with this one.
Anyway, long story short (yeah, I know, too late), there needs to be an alternate method of hurting enemies. Maybe an "Enemy Friendly Fire" quest rule even?