So the tool contribution to quality could be broken down into 4 parts 2.5% each tool equipped to the max total of 10% modifier from tools. But the minimum tool requirement could remain as it is you just wouldn't receive the bonuses to quality without the other tools equipped.
Moving into the MMO I think we need more things to make our profession choices feel different. And people performing them loof different. Its fine atm with most people running on servers that have higher skill caps. But when we are playing with 600-700 points and focused on fewer tradeskills. I think we will want to be able to have a way to "perfect" that choice. And working towards having a full set of 100q tools for our crafts would add a bit more "endgame". Perhaps minimum skill levels for equipping them would work nicely there also.
Probably need more tools than we have available atm to make this work but here's a few ideas for combos that I've come up with so far.
Prospecting Minimum: No tool
Modifiers: Shovel, Pick, Bag, Torch
Mining Minimum: Primitive Pick
Modifiers: Pickaxe, Torch, Shovel, Backpack
Smelting Minimum: Primitive Crucible and stick
Modifiers: Metal crucible, Tongs, Gloves, Mold
Forging Minimum: Primitive hammer
Modifiers: Blacksmiths Hammer, Tongs, Gloves, Plunge Barrel
Armorsmithing Minimum: Primitive hammer
Modifiers: Blacksmiths Hammer, Tongs, Gloves, Weaver's toolkit
there are many options and I could go on with every crafting line. But I hope you get where im going with this
