Take 4 vans to Washford with a class 33. Collect 4 more at Washford. Drop them off at Bishops Lydeard?
Don't really see DTG adding a scenario like that at all. That's totally the kinda thing that will be done by the community when an editor is released.
I was thinking more of an extra service layer RailDan. Going out at the start of the day, and a return at the end of the day. Clear of any conflicting passenger traffic. Having similar shunting features to the Huddersfield service in NTP. It would be dark in winter, but daylight in a summer (gala) setting. Could be a class 33, 09 or in future even a tank engine. With the vans being at their destination before passenger services have commenced. It would add extra rolling stock interest in the sidings. In fact to help this maybe have 8 vans at Minehead. Take 6 of them, drop 2 at Washford. Take the remaining 4 to Bishops Lydeard. Then the reverse at the end of the day?
Having a loco DLC for another route add services to a different route would definitely be a first, I guess... still don't see DTG doing it, but I agree it would be interesting to see.