Nice! You have a cool connection to it.
Mills are huge so it's good that you've thought about downsizing. I wanted to include a coke works on my layout but it was just going to be too much real estate. That brings me to my next point: use the walls. It looks like your layout is tucked into a corner with walls on two sides. You could use a 2D backdrop to "build" that coke works or any other building that you might want to fit but is too big (like an ore yard and crane, for example).
You'll be surprised at what you can accomplish with the Ross switches. It's also convenient that you can't go wrong with Atlas or Gargraves track (both work with Ross switches).