The best way to do this would be to break the route down into the real life driver changeover points so that you can do an uninterrupted part of a drivers on to off diagram. The route could eventually be covered with multiple route add-ons.
AFAIK, NCL, LDS, BHM, then not sure after that. EDIT, found a source for XC depots Cross Country - Bournemouth; Plymouth; Bristol Temple Meads; Birmingham New Street; Leicester; Derby; Cambridge; Manchester Piccadilly; Leeds; Newcastle; Edinburgh https://www.railforums.co.uk/threads/driver-depots.151508/post-3076081 Of course not all of those are on the route though
The Edinburgh to Newcastle bit is interesting to me with some interesting speed and gradient changes to negotiate. Sadly in the world of TSW I doubt we would even get that as a complete route. Unfortunately in TSW so much development time is taken up with detailed scenery way beyond what you can see from a train cab, collectibles and gimmicks which can be fun but ultimately make decent length routes infeasible. There is Newcastle to Edinburgh in Train Simulator Classic but it does have some serious inaccuracies for example Tudor houses in a council housing area, a missing palace in Edinburgh and broken level crossings. Still it’s better that nothing and a remaster of that might be a feasible way to start the route. Combining TSW and TSC could be the way to make this long route happen so a Newcastle to Edinburgh remaster in TSC, followed by Leeds to Newcastle in TSW. Then what would be the next section?
