Mark,
I took your idea and played with it to add a reversing loop and reorient the bench work, see what you think. The first siding section (including the tracks on either side of the switches) rises to 4" and the grade is 2.6%. The switch (including the leading track) and turntable rise another inch to 5" and the grade is 4%. There are only 2 flex tracks that need to be bent, but there are a few straights that need to be cut. I also reoriented the single access hatch so you could put a lift-out landscaping element on it. The aisle in the lower left could be changed to give you more area for landscaping. I also think the bench work by the turntable could be bumped out to allow at least 1 more leg. The 2 tracks along the top appear to be too close, so some work still needs to be done there. Personally, I think a reversing loop makes more sense than 2 turntables, but that's just me. 
