I would like to suggest the ability to allow Magma Blocks to be broken apart into Magma Creams.
The amount of exploration needed to find and harvest them in the over world can be somewhat substantial. I could see where the argument could be made that it would reduce the need to make it to the nether to battle Magma Cubes or Blazes to get/craft Magma Creams to be able to make fire resistant potions, but I think that is somewhat offset by the relative scarcity and danger with trying to harvest them. Also, unless you have been lucky to find a brewing station in a village or igloo you would still need to make it to the nether to kill blazes to make the brewing station to use them for anything.
It would also follow the way many of the other blocks than can be crafted from multiple of the same item can be split back into the item they were crafted from (nuggets <-> ingots <-> blocks for example).