TL;DR
Add a button to the train UI to copy the train to a new blueprint.Why ?
Creating copies of trains is annoying. Either manually recreate the train and copy the locomotive, or manually create a blueprint of the train.A dedicated button in the train UI would speed this process up significantly, especially if the blueprint was immediately inserted into the player's hand.
A bonus would be to also "straighten" any bent trains so they can be easily placed on a track.
Here's a mock up: