btw i am mostly just stuffposting
i agree, iron is too easy and too powerful for how accessable it is, and leather anything is overly annoying to get since killing the animals that drop leather, stupidly enough, isn't a 100% chance like lol
however adding more complex crafting and tool creation systems would just annoy everyone outside of people who like the mod and have experience with it, it would just needlessly complicate the game instead of an easy fix that'd help alleviate the situation:
make leather a 100% chance drop on cows and horses and rabbits (bunny leather)
make leather armor a tad more defensive
make iron spawn less often, like bruh it's as common as coal, one cave trip and you're loaded
make iron armor a little less defensive and make chainmail a little more defensive (currently both are the same, just one is rarer, but can be found when caving / exploring, so making it a touch stronger would be a little incentive other than collection)
making copper have tool variants would just entirely bypass iron in that reguard because it'll be another tool / armor set that's better than stone and extremely common, we'd be back to where we started, nothing being solved and just made more issues