I know it's not exactly multiple trains related.. While I want multiple trains, and transfer track, what I REALLY REALLY REALLY want is Switches...
So that you can have dual stations, with switches before and after the stations (ala Big Thunder Railroad in Florida), and also I want them so you can do reverser hills like on Expidition Everest, where the train goes up, stops and then goes back down, and is switched to a different track segment.
That would also allow for multiple trains as well..

Plus it would be really cool if you could build dual tracks, that the switch alternated trains on, so that after a train passed the switch changed position... For example.. say it was on L and then a train went by, and then it would be on R, then a train would go by and it would go back to L and on and on...
Just a musing from someone with some interesting ideas for coasters, that he hasn't been able to realize....\
CS