It would add more realism to have non-driveable HST on Darlington to Saltburn. Darlington seems unusually quiet. So doing this would make it a lot more lively. Also on the approach to Darlington, it would add red aspects as you wait for a HST to pass, as currently there are no adverse signals on the route due to the lack of traffic.
The same ai train could be used at Leeds. Although that would require a lot of work to create a realistic looking and sounding valenta, without it being driveable. Ive said before. Id be all for a BR/Intercity valenta pack. If it meant that I could run it on the ntp and have it populate stations such as Leeds and Darlington. At Leeds it could run a ECML/ MML ai service out of the station and off the route map. If I wanted to run a rare hst from man to leeds or leeds to man. A hst with 7 coaches could sub in for a loco with 8?