Weaponsmith, armorer and toolsmith should trade lower tier items

The weaponsmith, armorer and the tool smith should give weapons, armor and tools of lower quality than the current one. For example: Armorsmiths, instead of giving diamond armor on their last exchanges (and discouraging mining), they would give iron armor (with better enchantments to make it a more interesting exchange).

In the case of weaponsmiths and toolsmiths, diamond tools would be converted to enchanted iron, and those from earlier exchanges to stone or gold (or simply unenchanted iron).