I would object to putting all sub-surface routes under the one brand/name, other than the current set up of calling them sub-surface routes.
The current system of four distinct routes, with distinct colours on maps, provides a vital customer service function, in that it helps the customers understand how and where respective common train services do in fact operate.
I would prefer a re-structure of the sub-surface routes, including the following,
--Rename District Line, as Charles Line
--Rename Hammersmith & City line as Diana Line
-- Introduce two new ones. Charles Loop and Diana Loop. They would service the eastern side/end of Charles Line and Diana Line respectively, and loop around the circle line. Charles Loop shall be clockwise only, Diana Loop shall be anti-clockwise only.
I applaud this quite brilliantly scripted satire.