Update

Well, I've been sketching out some rough ideas for the new layout, and I think I know which version I plan on building. If I stick with the "simple" around-the-room helix, with the east and west Highland Line running in opposite directions, when they circle around to the staging area I can simple run the mainline down the middle of the staging area, creating the contiuous loop for running. On one side of the main will be the staging/storage for Hartford, and Waterbury on the other. My current benchwork is about 3" thick, and I'll add another inch or so for lighting the staging area. At a steady 2% grade I'll have about 10" minimum additional clearance, which I think will work well for staging. I will hide the staging from the operating location in the center of the room with doors, but it will be open on the staging side for easy access.

While the "double" helix created will be a little more difficult to build, it shouldn't be too bad. I plan on using the masonite spline method inspired by Joe Fugate and the method I used for the current layout. All of the flat sections (including the Stanley Works section which will be on a 1% grade) will use a simple table-top construction. I may just use OSB for the table-top, or I may decide to go with the foam.
All of the "tunnels" will be hidden behind buildings, and the staging will be completely hidden from the operators. I may or may not hide the Berlin Line as it ascends behind the eastbound Highland Line into staging.

The swing-open section will comprise track on several different levels, and will be 4 tracks wide. I will stagger the rails and use guardrails to help prevent derailments, and I'll use electrical contacts to create dead sections of track when the door is not shut properly. It will essentially be a half-height door with sections of track attached to the back of it.

I will have to work out the staging layout for maximum storage. At the end of each storage section I will install an inexpensive, manual Atlas turntable to allow turning of locomotives and cars as well as an escape track. I can create gantlet tracks to access the turntable to allow as many as possible. This will turn the stub-ended staging into a virtual double-ended staging. The alternative would be a transfer table.