Input Specific profession blocks (Blast Furnace, Smoker, etc)

I would like to see these blocks input slot restricted to only accept items that can be used in them.  Currently you can place pretty much any block in the top slot of the Furnace, Smoker, and Blast Furnace, but the fuel slot will not allow you to place items in it that cannot be used as fuel.  It would help players to understand what items can be used in which devices. I know I hate throwing a stack of cobblestone and coal into a blast furnace only to come back 10 minutes later and realize that doesn't work and that I have to use the traditional furnace to smelt stone.