I don't know what the minimum curve radius is for your Weaver cars, but I would suggest a single-track "hi-line" on fills and trestles like the P&WV/N&W as an O-72 or O-54 loop around the back of the layout (along the walls) with a siding to run your passenger trains and a through freight. To make the trains seem like they're going somewhere, make a backdrop that conceals a small 3 or 4 track staging yard. Maybe disguise the end of the backdrop with tunnels. Below the grade of the hi-line, you can have a point-to-point coal mine and timber road that interchanges with your hi-line. The coal road would probably have a maximum radius of O-42, and weave beneath the hi-line. If I have a free day later this week, I'll try to mock it up on SCARM.
Also, if you need any help, let me know, and I'll see if I can find some time on a weekend.
