I would like it for a mode where you can change ALL (apart from the one that will take you out of the map) of the switches and all of the trains are in the depo so you can do anything you want like a special service with 10 coaches and 2 engines it would be cool as you could start the train then drive it to a station (possibly couple some things) then drive the service before you say it is unrealistic it could be a new mode and you don't have to play it
The 'New York Switcher' on NEC isn't far from this. You can essentially switch and shunt as you please, within the playing area.