I remember sometimes stopping at a station and coupling to another train after which we continued as a longer train, or uncoupling and continuing as a shorter train. I love how the ICE has that ability with the nose cone opening but I never have any use for it in any scenario. Is there a service where this gets used and if not, could something like that maybe implemented? This would be a suggestion for any route really.
If DTG ever makes the route Dortmund - Hannover, there would be scheduled coupling/decoupling in Hamm (Westfalen).