Yeah, I've always liked the way DF made you double up underneath plate for exactly that reason. I guess what I'm trying to figure out is how much difference the different metal factors make for armor. Are different metals going to be better for chainmail and others for plate? Or with armor is it just hardness that counts, essentially?
The next version does have a "structural elasticity" flag to distinguish plate from mail. In practical terms, that probably means that, for a mail shirt or whatever, the metal's impact yield point (higher value = more resistance to blunt impact) is ignored, although its shear yield point (resistance to cutting) is probably unaltered. So if metal X has a high impact yield and low shear yield, and metal Y has a low impact yield and high shear yield, you'd definitely want to use metal Y for mail, and you might or might not want to use X for plate, depending on what your troops will be up against and how much protection plate ends up providing against blunt attacks.
Armor (and weapons) will be much more interesting now that there's no "one right answer." It's a good thing we're getting the new squad equipment interface at the same time, so that you can be all like "Quick, change into heat-resistant armor so we can fight off the fire imps!" without having to forbid everything.
Ok, I'd read that as adding "elasticity" from the item (plate/chain), on top of whatever elasticity the item had. So, for example, adamantine chain or cloth would have a bare minimum amount of elasticity (because it's woven of fine threads/links with some "give" to them) whereas adamantine plate would have none. Conversely, a "plate" item would have higher "hardness" but less "elasticity."
So it'd make sense, say, to make adamantine chainmail rather than plate, because adamantine is already hard enough and cut-resistant enough that making plate armor of it is gilding the lily (unless someone comes at you with an adamantine sword), while giving it some elasticity and give and cushion by making it into chainmail or cloth would make sense, since that way it'd resist bludgeoning some yet still be "harder"/ more "cut resistant" than any other material.
If I'm correct and that's how it works, yeah, things will get interesting -- the "right" type of armor will depend on what you have available and what you're being attacked with. For example, if you're facing a lot of goblins weilding iron weapons, and you'd probably want iron platemail if all you have to work is iron, but might be better off with steel chainmail if you could make steel.
DO you think that analysis is correct, or am I way off ?