Here I present you with the PAK and campaign folder for the experiment discussed the Game Help Forum. I change one thing, City#2 now sells steel instead of iron.
If your so inclined you can continue the experiment by changing City #2 to inactive & the script in Mission 2 to make City#2 active rather then inactive.
See how these change the flow of the campaign transitional & non-transitional buildings.
Weaponsmith = transitional
Bronze Smelter = non-transitional
Iron Smelter/Steel Furnace = transitional, but your unlike to see it with this setup. Maybe, you can figure it out and change the campaign or not.(shrug) Hint: the Campaign Creator Manual says something about Kilns dependency on clay being available to be place-able.