I think it would be great to be able to use the timetable in scenario planner. This would put ai trains where they are supposed to be and make scenario creating much less time consuming. It feels so awkward and clumsy having to create all of the ai from scratch. Perhaps also being able to choose your service from the timetable, substituting stock if desired with Off The Rails, would be a good option.
YES. Either this or the option to pick any train from the regular timetable (this would include what trains the AI Spawns with).