Dave Arquati wrote:

I doubt anyone would ignore buses/private transport and travel via
Oxford Circus. The Victoria line can't be extended at the moment
as it is already full to its capacity; the only possible extension
is a loop from Brixton to Herne Hill and back, as this would permit
a frequency increase on the line by avoiding the scissors crossover
at Brixton which limits capacity. The future relief promised is
Crossrail 2, which could drastically reduce Victoria line
overcrowding - but don't hold your breath for it to be built any
time soon.

A loop at Herne Hill is not the only way to increase capacity on the
Vic - a flying terminus would do the job just as well, without the pain
of turning trains around.

Interchange between the two stations will already only be about a
3-minute walk; the current White City Central line station serves the
are to the west and north, so moving it south would be inconvenient
to current users, and probably more so than the benefits gained by a
slightly-reduced interchange time. However, if the White City
development is very successful, it's conceivable that a new southern
entrance to the station might be built.

A southern entrance would indeed be useful to make it easier to reach
the western side of the White City development; however, it would be
expensive, and disruptive to the Central Line as well - there is
literally no ground space for the supports needed for such a structure,
as all available ground space is occupied by the scissors crossovers to
the east of the station. Building an access between the eastern edge of
the platforms and the nearby bridge would be interesting...