(eg. throw iron ore into fire get iron ingot, which will probably burn up straight away :D)

"throw iron ore" implies an item, not a block. Destruction of blocks via fire would be something more like "set iron ore on fire, turns into iron block"... apart from the detail that iron ore is not combustible.

Yeah, was thinking of items, not blocks - have updated the issue title. It's not a likely feature - just something someone suggested.