Separate Ore Processing into different tiers/tech trees.

[UndeadZeratul]

This way, it's not enough to just harvest ores and melt them down in the smeltery that's been sitting around since day one; players will need to build the required machinery to even process their resources.

Early game resources from the overworld will be able to be smelted down like they are today, in the smeltery, furnace, and blast furnace. Magical resources should require some form of magical processing (infernal furnace, mana pool, blood altar, whatever). Nether resources should require some form of tech machine to process them (RF powered crusher/furnace, etc). Ender resources might need the dragon altar or something to process them.