This isn't related to this particular version, but what are some thoughts when it comes to strategic resources? I find Iron in particular to be in a funny spot.
That's because it isn't hard to get 12 or more iron with just a few cities as you can find tiles that go upwards of 7. All the same though you can just as easily wind up with 0. Such is the nature of random map generation. However I do believe iron is the most prone to appearing in clusters (outside of coal that is, which can appear literally everywhere) and can be an issue for aluminum and uranium, which isn't so much the issue of clusters but more the issue of an entire continent not having a single source of it. But that's... yeah. Thankfully though iron isn't actually that big a deal because for the first half of the game it's only ever used by one unit (swordsman -> longswordsman -> cannon). Often times you have more iron then you need. Then I reach cruiser and minefield and all of a sudden I can't have enough of it. You need a lot if you want to be a dominant naval power. Unlike other resources iron has a considerable time gap between when it's first introduced, and when you unlock it's full repertoire of uses. There's aluminum too but that's a short period of time very late in the game and there's a building for that. Now I believe some time back the catapult and trebuchet also use to use iron, creating a split like horses had. IIRC back then the frigate also used iron and the tank as well?
I'm not suggesting we go back to any of that. If I had to guess that siege line change in particular was probably done to help make nice with the AI. All I'm saying is given the current balance if any resource was deserving of having a building, or a policy, or anything that generates an external source of it... It's iron. One thing I think is worth looking at is the hexxon refinery. Extra oil is nice. You need it for 5 frigging things. Coal however, well that coal wonder is (ok) if you aren't militaristic, but because there is usually so much coal on the map and due to their (thankfully) being a building to generate some if you are unlucky enough to not spawn near any, that the extra coal from this corporation on top of any other policies you may have picked often times can serve no further purpose other then to be a trade commodity. I wouldn't doubt it if that was in some way intentional. It's just the transition between switching out siege units for naval feels odd, and probably doesn't do the AI any favors either.
