Hi Chris D,
Here's something I tossed together in SCARM to help you visualize your ideas. A 30" wide around the wall with an opening in the center for peninsulas etc. Lionel FasTrack (cause I know it) using 084 outside, 072 inside, 3.5" from outside edge, 6" center rail to center rail spacing.
A 30" lift section on the end near the door and still maintains the walk-around as you designed it.
The track allows the big engines to run. With 072 switches and wyes to create access to a peninsula and changing mainlines.
You can reach everything and minimizes areas to scenic.
You don't really need a big solid space for the effect.
The SCARM file is attached.
Have fun!