CAMBRIAN 2 (from 3DTrainStuff) comes immediately to mind. It's steam era, covering a large area from Oswestry and Shrewsbury to the Welsh coast at Aberystwyth and along the coast to Pwllheli. Plenty of detail, with branch lines, passing loops and sidings galore. Lots of activities on the CD and in expansion packs. It's a great companion route to Bala Hub, which I see on your list.
You'll want to avoid Cambrian 1,though, as it covers the coastal route Aberystwyth to Pwllheli as it is today i.e. "rationalised" and thus stripped of almost everything of railway interest !!
Reawakening memories of train-spotting in the late 1950's and 1960's : Colne, Skipton, Hest Bank, Preston (Farington), Hellifield, Pilmoor, York South, Dawlish and Swansea. Great times!