Replace Diamond Tools from Villager Trades with a Special "Villager Tier?"

Currently, players are able to gain access to a virtually-infinite number of diamond tools through the blacksmith family of villagers. Not only do these tools always come with enchantments, but a player doesn't even need to mine or explore to get them. The only other uses for diamonds are 1. Enchantment tables, 2. Jukeboxes, and 3. Firework Stars. Therefor, reason to look for diamonds is greatly reduced.

The pitch:

Villagers will sell a type of uncraftable, steel equipment instead, which will fall between the iron and diamond tiers in effectiveness and durability. My thought behind this was Ferrovanadium, because of Vanadium's relation to emeralds. However, actually calling it that might be a mouthful, so a better name is probably in order.
The general overview would be that tools would have a tool speed of 7 (whereas iron has 6, and diamond, 8), 500-750 durability, be unable to mine obsidian (as to still require the players to progress to diamond), and do 0.5 points less damage than diamond tools. The armor would land somewhere between iron and diamond in durability, and lack the toughness stat.
For a long time, people have asked for "emerald armor." Assuming it is the case that people just want green equipment that is useful, this tier could fulfill that request despite the steel not being green in reality. Let them have their green, rich-man's armor.
Since it is steel, and thus consists of iron, smelting any of these items in a (blast)furnace will yield normal, iron nuggets.