Just adding my two cents here:
Railroad tracks: Wont it be a problem to make railroads require iron? I doubt we can make an improvement require non-integer amounts of a resource (Although I have no idea how LUA works in that regard, I expect it saves strategic resource requirements as an integer, and crash horribly when facing a float), and making each tile consume one iron is way too costly.
Wiring: Unrealistic much. Iron/steel was never used for wires, except as reinforcement for aluminium wires...
Building construction, Reinforced concrete: Practically the same concept. Maybe make bomb shelters / military bases require iron, or even mechanized infantry or guided missiles or maybe even make the new buildings people proposed here require iron?
Now highways and interchanges can be interesting, if we can come up with a viable use for them in late game...
Railroad tracks: Wont it be a problem to make railroads require iron? I doubt we can make an improvement require non-integer amounts of a resource (Although I have no idea how LUA works in that regard, I expect it saves strategic resource requirements as an integer, and crash horribly when facing a float), and making each tile consume one iron is way too costly.
Wiring: Unrealistic much. Iron/steel was never used for wires, except as reinforcement for aluminium wires...
Building construction, Reinforced concrete: Practically the same concept. Maybe make bomb shelters / military bases require iron, or even mechanized infantry or guided missiles or maybe even make the new buildings people proposed here require iron?
Now highways and interchanges can be interesting, if we can come up with a viable use for them in late game...