The copper/iron balance seems off. By the time I reached the end of my playthrough (roughly 50 hours) I had 2 large crates of copper but was always needing iron. I think the main source of this demand is the alloy frames using iron but I am not certain.
I think it would be nice to break metal scraps into two versions: steel scrap and copper scrap. This way you can harvest what you need and control your inventory better.
Another option might be to increase the copper sinks by moving some of the iron demand in recipes to copper.