SamB wrote:

On another note, I assume there's no intentions to ever do another
'extension' of the ELL into London Bridge from New Cross Gate,
replacing the Southern service completely? It makes quite a lot of
sense to me, and wouldn't be difficult to do if the ELL trains will be
mainline trains anyway.

You are right, it would not be difficult to replace
mainline trains from South London to London Bridge with
mainline trains from South London to London Bridge.