I think that certain routes, in this case NTP, are lacking a little in variety of types available to use. To this end I would like to suggest the following as a pack as dlc for the route. BR Class 123 dmu for express services (also could work with Diesel Legends of the GW). https://railcar.co.uk/type/class-123/ BR Class 124 dmu for express services. https://railcar.co.uk/type/class-124/ BR Class 128 dmu for parcels services (also could work with Diesel Legends of the GW). https://railcar.co.uk/type/class-128/
Pictures (for curious how they look like): Class 123 Class 124 Class 128 All pictures from Wikipedia.