I would love to see a standard class 4T tank engine which was one of the mainstays of 1950/60's steam on branch lines & shunting yards. I spent many a day watching these humble hard working locos in my youth. They would work well on SOS & PFA.
TBH, as much as I would love to see the Stn 4 and other standards in game, I do think it deserves its own route then it can layer on to SoS and Peak Forest
There is a name to describe them Belle because she's the Thomas and Friends 4MT locomotive. If you want to make it even better bundle this with an Ivatt 2-6-2 Arthur. They are suited for WCML Liverpool Lime Street to Crewe Crewe Basford Hall and Derwent Valley Line jobs That way we have more Thomas and Friends character locomotives MML and GWML has Pip and Emma HST Twins TVL GWML Legends Huddersfield Line Diesel Paxton and Daisy.