while a 80% iron 20% carbon should yield a stronger alloy
You'll need to work on your numbers, steel is typically 95% iron and about 0.5% carbon and the rest fillers of other metals to help with other issues, like protecting from rust or oxidation, keeping an edge, making stronger, etc...
Yeah, I'm not a blacksmith, I have some knowledge of alloys due to my experience in chemistry, but not that much, Besides, I'm writing more as an example of what can be done, not necessarily to use the exact numbers I posted in your (Leikaru's) game.
but that goes back to my previous post. Carbon is cheap, easy to get, and used in such small quantities, that you really wouldn't notice. It seems more like a feature upgrade, that you could focus on improving alloys, and express to the user which direction you are going in. but ultimately, it is a minor part of the game.
Perhaps you could still do this, but essentially just upgrade your mining stations to extract the new materials you need, but when very little is required, it should receive the same amount of attention.
You do make a good point - some common things, like carbon, should not be resources, I don't think I quite suggested that.
This can be done in a different way btw - not in terms of making some counter of supplies go up on your screen.
It's not quite the same, but in the Settlers VI (the only one i've really played out of the series) you had a lot of 'resources' (not just minerals) to gather.
There was wood, stone, iron, deer, honey, milk, fish, wool, wheat (that's 9 of them btw ) - which then got transformed on a one to one basis (by npcs moving back and forth) into secondary resources - sausage, smoked fish, soap, brooms, swords, mead, bread, banners, and a few others i think that I can't remember.
All of these resources were produced by individual houses rather than just having them gathered or transformed (by a baker, smoker, sausage maker, broom maker) etc.
It was more of a city building game than a RTS in a sense, and it did focus on resource management probably above all else. It had a very simplistic military in some ways.
Well, anyway, I'm not disagreeing with what you're saying, just giving another example of how lots of resources was done. I'm not actually trying to build one of these games, btw... just found this interesting.
By OP's (Leikaru's) description, I'm not sure if what he meant is at all similar to what I described, because as you said, his description is very vague.
Edit: By the way, I don't know why the Civilization series wasn't the first one that came to mind when you said ''more than 8 resources". While in Civ 4/5 they are not mandatory for victory, they are certainly very useful for both military and trade. Also, if you've ever played Empire Earth II - it has Food, Wood, Gold and Stone, and while not necessary during all other epoch, there's also tin, saltpeter, iron, oil and Uranium.