Thinking too fast now, but whatever.
Actually, I have been thinking of new ways to do metal. I like that there are additional metals in FuFo, but I'm not 100% pleased with the way they turned out, so I've been musing over other ways to do it.
I kind of like the idea of Atlantian Super Technology. Here and there, you might find pockets of lost technology. Probably nothing truly "super" but scraps of metal and rare gems, at least. There was an idea from a post-apocalyptic mod that I liked, that basically the world is littered with ancient landfills, buried in the soil. These would take the form of a "large cluster", like magnetite. The landfill is not valuable on its own, but the special metal ores and gems are generated only inside landfill clusters, like how platinum can be generated inside magnetite.
These landfills would be located in soil layers and be fairly ubiquitous. You should be guaranteed at least one landfill on a 3x3 map, maybe lucky areas have a lot of landfills, or a super rare landfill layer. I'll have to brush up on my mineral tokens to see what exactly is possible there.
Not sure how I want to handle the materials you find in the landfills. One approach is that the Atlantians represent modern day or near future humans, so their landfills contain materials like lightweight aluminum allows, high quality tool steels, plastics and advanced cloth. The furries that have inherited the world from the long dead Atlantians do not know how to produce these things, but they understand how to recycle them. Another theory is that the Atlantians had "everyday magic" something like Final Fantasy or Fairy Tail. In practice, probably not that different, but I would be less restricted and less guided in what I can come up with. There might be special buildings you can only make with tools excavated from Atlantian sites, like a thunder crystal that is the component for creating a thunder forge, which allows you to smelt aluminum and titanium, or a ghost turbine lets you create a building which provides free power for mills and pumps and so forth.
But that would be lots and lots of work, and let's be honest, I would probably chicken out and keep it simple.
The idea of Vampire Hunter Bats producing Super Silver makes me think it would be cool if every culture had its own special alloy, or perhaps just a special material, I'm not sure I would have enough good ideas for everyone.
Fox/Japan = Sakuragane = A highly refined form of steel, i.e. 2 steel bars + labor = 1 sakuragane bar;
Rabbits/England = ??? = They are vegans, so maybe they can make some material from plants that is usually made from animals. Plant leather, off the top of my head. Or maybe they can make leather out of metal? Chain leather?
Goanna/Egypt = ??? = Maybe an enhanced form of bronze;
Eagle/Mongol = ??? = Might have special abilities to make things without plants, like a carpenter shop that uses bone, or just convert bones to "bone logs";
Lobster/Viking = ??? = Probably something from Viking mythology. Red Gold?
Gazelle/Zulu = ??? = Maybe a poisonous, but I recall this being tricky to implement; Enhanced leather also springs to mind; Or something medicinal, if that's possible;
India/Cobra = Wootz = Probably same as Sakuragane, highly refined steel, or steel with an extra ingredient that strengthens it;
Monkey/China = ??? = Surely there's something from The Journey West; Maybe something to do with silk; Maybe something to do with Chinese Alchemy;
Salamander/Wizard = Rune Metal = Probably something that is intermediate between iron and steel, but the salamanders can transmute any metal other than iron or steel into Rune Metal.
Badger/Diggers = ??? = I still kinda like the idea of Ethanol Coke; Maybe something to do with gold, like they are gold diggers;
Bat/Vampire Hunters = Super Silver = I'm thinking it's basically steel, but made of silver instead of iron. Probably still heavy like silver. I would probably retain FuFo2's mechanic that you need sterling, not raw silver to produce weapons, so it could just be a way to weaponize silver without copper.
???/German = ??? = Theoretically, there's some equivalent of German Silver. Paktong would still be available to all, so maybe German Silver or Nickel Silver is a more valuable form than Paktong.
???/Roman = Super Pewter = Something to do with lead, for sure.
Ideas with no placement yet, a lightweight metal (although Aerochalcum is this), lead into gold, ability to spin metal into cloth, or some enhanced type of silk/cloth/etc.
To recap, the previous FuFo metals were: paktong, real life cupronickel, comparable to bronze or iron; dragon-fossil/dracometal, enhanced paktong; pyrochalcum, extra sharp iron; geochalcum, extra heavy iron; aerochalcum, extra lightweight iron; hydrochalcum, blue gold; blaze/rock/cloud/ocean steel, steel alloy with enhanced sharpness/heaviness/lightness/value; novachalcum, i think is basically tungsten carbide; pyro/geo/aero/hydrochalcum were found in small clusters in igneous layers. So you were basically guaranteed to find some, but they could be difficult to exploit in large scale. Combining one of each Xochalcum resulted in 2 bars novachalcum.
I think paktong is fine the way it is. I might see if I can make dracometal more like a metallic bone, instead of just multiplying paktong's stats. I don't like how pyro/geo/aero/hydrochalcum can all show up in the same place, and I want to exaggerate their properties a bit more. Instead of elemental steels or bronzes, I might allow you to produce "refined" versions using some other esoteric ingredient, bones, logs, sand, clay, silk, etc.
I've been thinking of making an ore called "deep iron", which appears deep underground, or at least not in sedimentary layers, so you don't have to rely on specific environments for iron/steel production.
EDIT:
Jotting more ideas down. I guess I'm also interested in expanding the number of real metals available. Even if I keep the 1399 tech cut-off, there are still a few metals that were sort of known to science.
Arsenic was known as a poison component of orpiment and realgar since ancient times. Arsenic can be used to create
Arsenical Bronze. Arsenic is also alloyed with lead, I'm not sure why.
Antimony's ore Stibnite was used in cosmetics, and it rarely exists as a native metal. Antimony is used instead of lead in modern pewter, and it can be alloyed to lead to increase hardness.
Chromium and Cobalt were sort of known in ancient times, but not as pure metals. They are difficult to extract from their ores, and are often the chief components of "super alloys" along with nickel. They would be kind of a cheat, but an interesting one.
Magnesium was not at all known to ancient people, but it is a chief component of magma (as is aluminum, supposedly). In a culture with such a close relationship with magma, it might be interesting to develop some way of extracting magnesium. Magnesium is lightweight but strong, akin to aluminum and titanium, but also flammable and chemically interesting.
(We discovered in some previous episode that the carbon fuel from smelters decreases the melting point of iron and gets absorbed into the metal to create low-carbon steel. But magma has magnesium in it, which purifies sulfates from iron and steel. So a charcoal smelter and magma smelter would actually produce different grades of iron. )
I'd be interested to find more alloys of bismuth, but it seems like it's not popular in modern metallurgy. I removed bismuth bronze from FuFo2 in order to clean out less useful alloys.