Describe the solution you'd like

There's a config option that allows you to set which mobs can spawn with Metallurgy gear equipped. However, a nice addition would be to enable/disable which gear types mobs can spawn with in the first place.

Additionally I would love to see a blacklist option implemented for Etherium Armor's set bonus that prevents them from passing through certain blocks.

Why would you like this to be implemented?

It is nice that mobs can spawn with Metallurgy armor, it adds some difficulty and variety. However, this can easily be abused by using a mod with a mob spawner and farming all of the rare metals in the world by repairing and re-melting it in a smeltery. (In my case: Draconic Spawner, Cyclic Anvil/Repair Talisman/Actually Additions Repairer, and into the Tinkers' Smeltery).

For the Etherium blacklist, this is a case similar to the Staff of Travelling from EnderIO: You can set a blacklist that disallows Travelling through blocks such as Bedrock, Labyrinth blocks (Twilight Forest, Atum, Erebus mazes), Thaumcraft Warded blocks, RFTools Force Fields, etc.