In an earlier post, I mention the Cambrian Railways as a possibility. It's now a completed project, and available for purchase. In this post I'll give an outline; then in further posts I go on to discuss some of the questions and problems I encountered in research.
The Cambrian Railways system was formed from the coming together of several relatively local companies, and it was always locally based. Much of its mileage was single track, but that trackage was used quite intensively. The main line ran from Whitchurch, on the LMS line from Crewe to Shrewsbury, through Oswestry to Welshpool, then on to Montgomery and Newtown, continuing via Machynlleth to Aberystwyth. A secondary main line continued from Dovey Junction around the coast via Aberdovey, Barmouth, Towyn and Portmadoc to Pwllheli. There were several other branches, including one from Moat Lane Junction, a few miles west of Newtown, to Brecon.
I looked at the possibility of covering the whole Cambrian Railways system, but that was simply too much to handle; it would have needed well over 20 screens! So we've ended up with 15 screens covering the main line from Oswestry to Aberystwyth, together with some quarry branches near Oswestry. Maybe the Coast Line will come later.
The two major engine sheds are Oswestry (89A) and Machynlleth (89C), but there are also subsheds at Aberystwyth, Moat Lane Junction and Welshpool.
Most wayside stations have a small good yard, served by at least one pair of pickup goods trains each day.
The line was constructed on a limited budget, and in GWR terms was mostly a "blue" route, meaning that heavier engines were not allowed; in fact it was for lines such as this that the Manor 4-6-0 class was introduced, with power not much less than a Hall but a lower axle load. The various branch lines often have a lower route availability, some "yellow" and some "uncoloured", so it is necessary to be selective in which engines to use on which lines.
Though there are fewer trains running the full length of the line than on say the Waverley Route, I think dealing with the various branches and planning crosses on the single line will keep the operator equally busy.