Yeah, I like that idea. I was also thinking that it would be awesome to implement carriage decoupling so that the train could move to a turntable, turn around and then recouple on the other end of the carriages. I don’t like it how trains can change direction on the spot.
This way, you could leave the carriages at the station to be filled with cargo etc, and have the train arrive with empty carriages, uncouple them and then pick up the full carriages and head back. Passenger trains might work differently, but the train would be able to move backwards so you could implement zig-zag tracks to get up steep hills as well.
As far as capacity goes, I think it’s just as many trains/vehicles that can fit on your screen, since there doesn’t seem to be a scroll feature on depots for some reason.