currently there is not a true problem with the system in place but with these changes it creates more of a tech tree for people to explore and move up. As it currenlty stands there is really just primitive tools and metal tools.
I would like to see primitive tools, copper tools, bronze tools, wrought iron tools, and finally steel tools.
I base most of this from a minecraft mod i play called "Terrafirmacraft" which has such a tool tree. their system also has a balence system of having to create better furnaces to melt the metals. copper and bronze can be melted over a fire at low tempetures so early tools are possible but very weak. iron must be melted in a furnace and be hammered out of the iron bloom formed from this process. finally steel can only be produced at high temptures in a blast furnace which in game is the equivelant to a bloomary.