Big Steel
Before I make a couple of suggestions, I must say that I am not a devotee of big-time modern and/or industrial railroading. The world I love is late 19th century logging and short lines. I also have a tendency to simplify track plans and get rid of any track that doesn't have an operational or scenic purpose. This may not be what you would want. So think about my suggestions before implementing any of them - you may have a better idea.
- lose the bottom 2 or 3 yard tracks at the steel mill. The steel mill yard over-powers your main yard, and there is no real separation from it. Leave the space where the tracks were empty, or put some low structures there. This will provide some visual separation between the main yard and your steel mill area. I don't think you need that much car storage at the steel mill (but could be wrong).
- your main yard has 4 double-ended tracks, plus 3 single-ended tracks. Unless you are storing complete trains there (staging), or have a separate operator running the yard, 3 double-ended should be sufficient. One track will be the through main line, and the other 2 would be arrival/departure tracks which could also be used as a passing siding. The single ended tracks are your classification tracks. The double-ended tracks should be shortened to your 6ft train length. This will emphasize your main line a little more.
- I'm not sure what the purpose of the passing sidings at the bottom of the plan is. If it is a town, it only needs a single passing siding with a few spurs. The passing siding needs to be 6 ft to match your train length. Again, fewer unnecessary tracks will make your layout look bigger and leave more room for scenery and structures.
- I'm not sure that tying the mine to both sides of the main gains you anything. I personally would make it a single-ended branch, like you originally had. The track arrangement at the mine is great - just adjust the run-around lengths to the length of the cut of cars the mine will be handling. They don't need to be longer than that. The tail length may be just an engine length, or an entire train length - depends on how you want to switch the mine.
- The odd spur could be where mine tailings are dumped. Or could be a team track where supplies for the mine workers are brought to.
- 2-3 tracks for staging is a great idea if they will fit without messing up the other elements of your layout. This will allow you to bring intact trains on/off the layout. They, too, need to be 6ft long to fit your trains.
just my thoughts, it's your layout and choices