can i for instance take some coaches or wagons from newton heath on NTP and take them to that huge empty sidings in Huddersfield and leave them there. Then get an engine from Leeds drive light engine to Huddersfield sidings and pick them up and take them to leeds. Q2 can i copy and paste wagons or coaches and fill them sidings up in Huddersfield
As I understand the game mechanics of the scenario planner, we won't be able to leave a consist anywhere without a loco. Taking this into account, we won't get permission from the signaller to access any part of the track where another train is waiting. Think again, it just won't work!
...the best choise for a passenger service on OSD would be a Calltain "Baby Bullet" with its newer double-decker wagons. Because in reality Go Transit serves this route with the same kind of trains, but in green white company colours. So the Scenario Planer makes at least this combination possible.
A nice idea, but ... I've seen only one yard with manual switches and with AI driven locos, that is Sunnyside yard on the NEC route. And it doesn't work well, the probability that AI commands for these switches will interfere with your intentions is pretty high.
I wrote ... In scenario planner you'll have to send your AI train there, otherwise that yard will be empty.
Alternatively you could start your trains in the sidings and give them a start time way after you should be finished, that way they should never move. (Provided there is a starting point to plonk them there)