Hi Sean.
Sorry to reply so late, but I've been busy lately.
I had been going to suggest something like the attached image - forgive the crudeness, but I only had a moment to scribble something down.
In the image, I've shown the roads with a kind of orangey-brown highlighter, I've omitted the turntable, and I've left the left hand side of the run around loop off-scene, allowing you run longer trains in and out, and simplifying the pointwork a little. This would mean running two tracks through the hole instead of just one, but I think that you have two tracks just outside that hole, so you lose a bit of functionality by having only one track entering anyway.
All only suggestions, so no offence is intended.
Also, rather than an embankment on the left hand side, how about archways? You can still run the road along the top, as I get you, the cars need to be shown off, too. But, you don't lose much space on your board, and you get to run a dummy line out through one of the arches if you like, where you have the Evergreen with the hot box in one of your photos.
I know now that the hill in the right corner is pivotal, and staying, so maybe a tunnel cut into it?