Personally, I would prefer it if we didn't have Qyburn at all. His only positive trait is that he's politically toxic and thus dependent on Cersei for his continued survival. The problem is that he's politically toxic for a good reason. Magic in ASOIAF is generally based on human sacrifices. I will not expand on the moral argument against human sacrifices because, I hope, we can all understand why human sacrifices are bad but there's also the political argument that allying with the Faith while accepting an aspirant necromancer as retainer is a bad idea.