How about the second Welsh route? This route can be fro Cardiff Central/Coryton/Rhymney - Aberystwyth/Pwllheli/Wrexham Central - Chester. Year: 2008 Rolling stock: Class 150, Class 153, Class 156, Class 158, Class 57+MK3+DVT all in Arriva. FGW liveried HST layered in from GWE. Class 66 in GBRf Livery and DRS Compass and many freight wagons.
There is no direct route from Rhymney to the Cambrian Coast. The only way to integrate what you ask would be to include the South Wales Main Line to Newport, off up the North and West to Shrewsbury (for the Cambrian) then across to Wrexham. Which would be far too much for a TSW route, probably getting on for 300 miles.
You’ve suggested 3 routes there. Cardiff Central to Rhymney Wrexham General to Chester (trains from Wrexham Central only go to Bidston) Trains from Aberystwyth and Pwllheli merge at Machynlleth (no direct service between both) to Shrewsbury and Birmingham New Street
Pick one of the three proposed routes and go into detail on it. Imagine you were going to quit your job and work on this route full time as a developer. What would be GOOD enough for you to quit your job and wager your future on it selling well?