What I propose is a spiral layout with two decks and helices linking up. You therefore have a fiddle yard leading onto a gradient (PowerBase etc. might help) with a passing loop/halt on the climb to a terminus. The terminus would benefit from a 3/4ft long platform (might be able to stretch it, I will double check this) and a goods yard. Please see enclosed photos of the track plans: The passing loop(s) points are setrack but the station would use streamline. Anything you want for the FY.
I suggest 2nd Radius curves if you can accept them. In 1077 trains didn't exist...
So, now to the tour of my plan:
We start at the top, with your terminus station.
You will find 3 platforms, with another siding to access the kickback siding. The two could arguably be freight. The bottom of the plan is characterised by the loco depot and long siding (you could wire up a few isolating sections on the long siding or use it as a carriage siding.
Followed by a couple of spirals. Please note that this deck descends anti-clockwise.
On the next deck down, you will find a loco shed with an additional storage road and a double slip, linking on to two tracks close to each other. On the long loop, you will find a loco release siding for station to station shuttles. The long siding could be for anything- an industry of choice, P-way etc. This siding is perfect for this as you will find that quite a bit of space has been left there for a sprawling complex. This loop should be enough for the longest of trains, managing a 2+5 HST (Just)
As many loops as wanted
The fiddle yard features no less than six medium length sidings, 2 long ones and 2 short ones. In total, 10 trains can be stored in the Fiddle Yard, plus a loco in the release siding, up to 5 in the middle MPD, one train on the passing loop, one on the platforms and up to 3/4 in the station/MPD (some trains, some locos). This allows a minimum of 20 locos of which 7/8 are trains on the layout at any one time- who could want more?
There is, however, a catch: The gradient layout will require lots of time/money to build and could make it a bit heavier to move, not to mention more fragile. I am not really trying to market this type of plan, but show the extremities of what's possible. Just have fun!