Charles,
Here's what I came up with using the original space and design. As you can see, I wasn't able to do much with it.
I wasn't happy with it, so I decided to try something with Jan's around-the-room approach, Unlike Jan suing O-36/O-45 curves/switches, I incorporated the design from your photos and retained the O-45/O54 curves/switches. However, unlike the original, it allows 2 trains to run on separate loops; O-54 on blue loop, O-45 on both loops. I tried O-72 curves on the blue loop, but they didn't fit. One train can be running on the blue loop unattended while another works all the gold spurs.
Anyway, I reconfigured the entry to eliminate the curve on the lift-out. I also added an example of a simple lift-out (right side of photo). The greens are the decking, the browns are framing, the orange are cleats and the gray are alignment pins. The 3D photo show what it would look like. The pins in the 3D Photo would actually be hidden.
