I am suggesting the Cambrian Line from Shrewsbury in Shropshire to Aberystwyth and Pwllheli in Wales. It would be both the first Welsh route in TSW and the first UK route to include ETCS after appearing in the Luzern route. Rolling Stock would be the class 158 in TfW livery.
Definitely 110% agree with you one of my favourite units they did the class 465 for southeastern to faversham route