Paul,
Here are two concepts to start you thinking. Both have a minimum curve diameter of O72. The spacing between the two mainlines is 5 inches. I left space for the door to swing in at the bottom of the layout. If it is not needed the space can be used for industry around a waterway.
There is plenty of room for industry and scenery in the lower right. the two mainlines cross over each other in the center. Reverse loops can take advantage of this.
This concept leaves the entire center open for a yard complete with a turntable. The mainline can be shifted diagonally to make room at the doorway for a lift out section.
Jan