Here are some pics of my prewar layout, its 10 x 7, and contains both standard and O gauge. It certainly can be scaled for your desired size. Currently I can run 4 trains at a time and have 1 additional standard consist in waiting.
The inner O gauge loops allow for 2 smaller consists to run independently or 1 larger one on the connected loop. Also the switch placement was sized to allow me to remove the 2 closer track circles and replace them with a crossover track to form a figure eight.
For Christmas my wife bought me the terrace and station. This required me to change the inner circles to a circle and an oval to accommodate the new addition.
Hopefully these will give you some additional ideas, keep us posted on your decision and build.
