Why is the proposed new HS2 station at Birmingham being planned as a terminal? Surely the long-term plan is for the line to be full-length through to Scotland.
Building the station as a through station would make better economic sense, so how about building this new station like Stratford International, in a deep cutting? Then, at the Birmingham end, have two connecting tunnels under the city until a surface connection is practical.
Yes, it may be cost more now, but in the long term it would make sense.