Why are there better connections between Thameslink and the deep-level
lines? The most obvious example is a new station on the Central Line
where it passes underneath the line, with the possible closure of
either St. Paul's or (less likely) Chancery Lane. Does the Central
Line lie at an inconvenient distance for Farringdon (too close for a
discrete station, too long for an interchange)?

A unified station at Elephant & Castle would also be a huge benefit,
especially as changing trains is a time-consuming and intimidating
process for many.