Lichfield Trent Valley to Birmingham New Street, this route could come with the class 350, class 323 and maybe a DLC possibly an extension to Redditch, I think this would be really nice in TSW2 if added
The biggest issue this route would have would be a lack of AI or lack of correct traction AI services at New Street.
Regardless of era just consider all the different service groups and associated train classes. HST's, Voyagers (220, 221), Pendies (390), various DMU's. If you go back a few years, WCML loco hauled, Cross Country loco hauled, even more types of first gen DMU's. It would end up like Cathcart Circle, a vast but empty station.
I mean there's loads of stuff you'd see at New Street that isn't in TSW at the moment, so it would look deathly quiet or totally wrong using loads of fictional units