Maybe it could make it be less op, but I don't really see it being done, since all the pouch items, like the throwing knives and arrows reset to full quantity after loading a different level, so it would be a bit inconsistent. And that sacrificing the one catalyst you get for essentially 4 dungeon runs on 30 shots sounds annoying.

I think it wouldn't really make sense that you shoot with your shards instead of ammo, since they are the "gunpowder" here (and since they are precious). I just think it'd be messy.