Well, that's looking pretty good! I like the yard by pass too.
Rico mentions a customer for the coal mine. I wonder what industry you might include to deliver coal too?
One idea might be a power station. Another is a coke plant. Or maybe an export terminal?
Coke plants are interesting. They take coal in and produce coke (of course
) but also produce tar and chemicals as by products. So you could have reasons for tank car operation too. Also there is often dedicated switchers for the coke plant.
The coke might be sent to a steel mill represented off layout with by staging tracks and the tar could go to an asphalt plant, which is small enough to fit on your layout.
Walthers has two coke retorts/oven kits. One for their gas plant series and one for their steel industry series.
Researching industries has become a favourite pastime for me as a side effect of model railroading. I know much more about industries than I once did. Anyway, just ideas for you to think about,
Paul