Just reading an article about Thameslink progress in the latest Today's
Railway UK; the author writes:

"One issue still being debated is whether to grade separate Metropolitan
Junction, where FCC services now leave Southeastern's intensively used LB -
Waterloo line for Blackfriars."

I would have thought this problem [of Thameslink & SE services crossing] had
been completely designed out by moving the crossing point to the diveunders
east of London Bridge, and then having dedicated pairs of tracks westward of
London Bridge for both the Blackfriars and Charing Cross routes.

Was a grade separated Metropolitan Junction a fall back proposal if four
tracking through Borough Market proved impossible?

Paul S