I would love to see the currently used 801 on Fife Circle except it would be able to be driven as far as haymarket, just like the 385. Currently, LNER are doing services from London Kings Cross to Glasgow Central, so it would be a great addition to the route. I think that adding services that go as far as Haymarket from Edinburgh driveable would be a great addition. I think this would make Edinburgh a much popular station on the route and it would create more opportunities for the route.
u clear dont know about the fife circle mod timetable for TSW4 on PC it has the class 801 witch has been turned into the class 800 witch runs on there for real
If I'm not mistaken, there's also a select few LNER trains which go along the circle between Aberdeen/Inverness and London via Edinburgh as well, although without the 800 this is unlikely.