If you're going to do that, then take a look at this for some more ideas. The turntable is a Millhouse Rivers 28" with an Atlas 3-stall roundhouse. I know the right grade is too steep, but the siding could be moved to the apex of the loop and the grade reduced. I did the best I could using your 4-way switch. I didn't know what all the buildings were, but I left them in.
Anyway, just more food for thought.
