I think it would be interesting if we could have an off the rails option in service/timetable mode so that we can substitute any train/locomotive to run on any route in lieu of the realistic train/locomotive. For example, on ECW we could have Off The Rails substitute the 377/4 with the 166 or on GWR we could substitute the 43 with the DB BR ICE 3/3M. This way we could use any train/locomotive to run any service. Some trains/locomotives might be unsuitable e.g. too slow to meet the timetable, but it would still keep things interesting and would save us having to build scenarios to use our favourite trains/locomotives even though this can obviously remain as an additional gameplay option.
Or maybe, for those who might not want it all the time, you'd be able to choose what trains can be substituted for each route, which would be useful in a situation like this: Route A (let's say it's London to Bedford) has the Class 700 included in it. Route B (let's say London to Brighton) doesn't. The Class 700 is commonplace along the Brighton Main Line, so being able to let it substitute for Class 377s would be an improvement, even if they'd have to go into London Victoria/Bridge. This could help avoid the issues Train Simulator had when identical trains were available both as a separate add-on and included in a route (I'm looking at you, Class 319). Of course, this wouldn't be necessary if trains in route DLCs could have services/scenarios on different routes.
IIRC Matt said the issue preventing this is that the AI gets the same selection as the player does, so if you allow all trains then the AI will spawn in a completely random train, if you limit what trains can be used then we get the substitution we have now, but IIRC they said they are working on a system which will give the player more freedom while "locking" the AI to the correct trains.
I would like it if the AI was a mix between the “correct” train and the other trains the player picked.
If we allow the player to pick all train you allow the AI to pick all trains, not the just the one you picked + the correct one...
This would be great. You wouldn’t have to fumble around with the scenario planner trying to get AI on the tracks as well. The AI would be more diverse than normal with this, and it’ll make certain routes (like the German ones) more realistic.
It would be great to see the option to use the timetable for AI trains. This would use the normal services available with your service supplementing them. Far less long winded and confusing as building your own service and then trying to work out all the others too.