This idea has already been discussed here on the SnR discord.

Currently, as far as i am aware, there’s no way (without CC) to rename a train without the player having to enter the desired name into the station block when the train is stopped there.
Given that S&R adds the ability to disassemble and reassemble automatically i think it’d be fantastic if it also supported renaming a train.
I might try adding the feature myself if there’s no objections to it, but no promises there.

How I propose this should work:
When a deployer holding an unnamed nametag “right clicks” on a train station where a train is parked, the name of the train should be copied over to the nametag
When a deployer holding a named nametag “right clicks” on a train station where a train is parked, it then applies the name on the nametag to the train.

An additional request, which could also easily be done through a datapack myself if you guys don’t like the idea:
Add a washing recipe for nametags that “scrubs” the custom name off the item and returns it to an unnamed nametag.

If implemented as suggested, this would allow you to copy the name of a train to a nametag as soon as it pulls in, then disassemble the train and do whatever you need to do (a turntable for example) and when it has been re-assembled, apply the old name back to the train. After this you can send the nametag into the washer so it’d be ready for the next train.