It may be easier to do 2 separate ideas .
Ckt 1 ... Main line , a loop with open staging so you can send a train in either direction .
Ckt 2 ... inner industrial trackage to be worked by a Shay , 44 tonner SW's etc .
The interconnect between the two is optional , and if at the staging of ckt 1 , you had ckt 2's couple track yard , a simple cross over is all thats needed to interconnect ckt 1 with ckt 2 .
Ckt 2 could be anything and any radius . Logging , City , Industrial , Rural Manufacturing , Stock Yards , Sea Shore , you name it . If it is outskirts of city , the trackage can be quite complex .
You can have each ckt in different levels as in 2 separate layouts.
One ckt can be passenger , and the other one freight .
Each ckt can be a different railroad .
An center peninsula industry with a Y connection to both directions .
I know this isn't a track plan , but it may be options that you didn't think of that will lead to a track plan .