I just added it in via script editing:
Config STONE_MAIL; { StrengthModifier = 600; DefaultSize = 75; DefaultMainVolume = 30000; BitmapPos = 16, 128; Possibility = 50; NameSingular = "stone cuirass"; FlexibleNameSingular = "armor"; MainMaterialConfig = { 5, LIME_STONE, OBSIDIAN, MARBLE, BASALT, QUARTZITE; } MaterialConfigChances = { 5, 500, 250, 200, 100, 50; } InElasticityPenaltyModifier = 40; EnchantmentPlusChance = 2; TorsoArmorBitmapPos = 32, 416; ArmArmorBitmapPos = 80, 416; AthleteArmArmorBitmapPos = 80, 448; LegArmorBitmapPos = 16, 416; }The idea here is that stone armor is its own thing, and very rarely found. It has a very high strength modifier to compensate for the fact that stone materials aren't actually that strong, and to counteract that I've added an obscene main material density to make them extremely heavy. With a little extra testing and tweaking, and the addition of something to stop people changing their materials I think we could make this work.
Currently I think the main material density is still a little too low - I'd want it to overload most characters.
I'd be happy to make my own sprites for it too if everyone likes the idea.