That's in one of the "Klambake" layout books I have. The problem with H.O. plans is that, while you can double them from 4x8/5x8 to 8x16/10x16, they become unwieldy because of the reach factor and need to place access hatches. The hot ticket would be to convert it to an around the walls design. At the same time, you can bump up the curve size to be better suited to the Ross turnouts available.
Breaking it into elements is a good start as you can place these elements into the layout room. I would take the Highland branch and run that as a graded branch along a couple of walls and put the wye in the corner in a mountain through which the mainline would run.
