Allow us to rearrange creatures
Now with some of the tribal lord types in Ixalan, it's even more important than ever to have our creatures on the field in the proper order. This can be frustrated by either having a creature destroyed and the new cast version ending in the third spot, or by the order in which you draw them. For example in this new set, Captain Lannery Storm needs to be in the bottom slot, else she won't make a treasure before your other pirates attack, and none of them will get her boost. Additionally with Mavren Fein, you need your pile of vampire tokens in the third spot so any reinforced vampires can buff them before they attack.
It would be helpful to be able to either rearrange the creatures, or, if that creates too many potential issues regarding rearranging because of defenders being played, perhaps we as players can choose which of the three slots we want creatures to live in when we cast them. So a creature is cast, and we can place it in the second or third slot and now have it default always to the first.