Surely this can be fixed. The production line must be capable of still building more coaches to extend to 12. Or will this cause massive issues with software etc.
I hope Siemens trains aren't as picky when it comes to modifications as Bombardier trains. I'm sure there's an option to build more carriages if needed, and possibly even entirely new trains. Certainly the coach numbering on a RLU suggests it could easily be converted to a FLU.
The trains are based on modern tech, unlike the Class 387s that are a weird hybrid of old and new, and still have ancient PC hardware to manage things. Plus they have buttons that keep falling off. (Mustn't forget to mention the buttons...)