Azrael: true. But still it would save a lot of time.
It should be possible even with trains. Just update the way how return to depot works. Instead of going straight to depot and getting stuck on crossings etc, just let the train follow the schedule until it is one crossing from the depot. I dont know how other people, but I have one depo next to each line. So as long as the train is following the schedule, it will pass next to depo eventually.
i know that not everybody has it build this way. So maybe two buttons “rerutn when possible” and “forced return” would be needed. One waiting for the depo to be one crossing away. Second leaving the schedule a pathfinding its way to nearest depo.