On page 116 of

https://consultations.tfl.gov.uk/tub...port_final.pdf

is a simple map of South London. It seems to have been thrown together,
not least because it shows the Catford Loop calling at Brockley, which
I'm sure is a mistake rather than a proposal for diversion, but also the
double interchange blob at Blackfriars has Friday afternoon written all
over it.

However, I'm interested in the Streatham Common Hub. It seems to be
suggesting that new platforms would be built on the Thameslink tracks
(Streatham to Tooting / Eastfields) but not on the South Central tracks
(Balham to Eastfields). But the new Thameslink platforms would be a long
distance from the current station, so I'm wondering if the existing
station would be moved northward past the junction, in which case the
Streatham - Streatham Common stations would no longer be able to call at
it (I assume the curve to Streatham is too curved for platforms).

I have to say, looking at a map I struggle to find many journeys which
the new interchange would allow that you can't do now by changing at
Streatham. But without fully understanding the frequencies of all the
lines, I can't say how how inconvenient or possibly unusable the current
interchange is.