Following what I said in GWE Expansions, I thought that Northern Trans-Pennine (and for that matter Tees Valley Line) could probably do with upgrading. For starters, they could add more BR locos of the time (maybe the Peaks). A thing that might be hard to do but would be nice is Transpennine Express Services (DTG has done enough licenses before with First Group) and maybe also Northern services.
NTP already has Peaks, if anything it could do with 25's as they habited the route at the time, certainly the Manchester side anyhow. Chances are slim to none nevertheless as they'll concentrate on the newer routes as they come.
I do really like the peaks but a 25 would be nice- maybe also 185's and the Nova 2/3 (Class 397 and Class 67+MK5A Coaches respectively)
Based on the reflected era, best options are... Class 25 Class 31 Class 123 Class 124 Class 128 Class 141 Class 504 with Bury extension
The addition I would like to see is Felix the Station Cat at Huddersfield, strutting up and down Platform 1. Not strictly correct for the era but would be a nice homage to a much loved character.
