Items with a "/" in their item ID don't seem to work. For most mods this isn't an issue, but mods like TerraFirmaCraft keep their item IDs sorted such as "tfc:metal/sword/steel" for a steel sword or "tfc:metal/ingot/copper" for a copper ingot.

Another nice touch would be the ability to remove items/equipment before our custom item/equipment is added. Some mods spawn mobs with swords or armor and override helditem and armor rules. A little more control over those mods would be helpful.