The Charing Cross branch could run along the original planned
Fleet/Jubilee line route via City Thameslink and Aldwych, and take over
the abandoned
Jubilee line tunnels and platforms at Charing Cross. I understand that
provision
was made for Jubilee line platforms when City Thameslink was built.

Not sure about that one - hadn't the Fleet Line been abandoned by the late
1980s? Would this route lead to the return of a service at Aldwych? If so
could they add a subway to Temple?

The idea of the Fleet/Jubilee line extension to the city was presumably
abandoned some time before the current extension further south was built.
IIRC, the original Fleet line plan was to include stations at Aldwych,
Holborn Viaduct and Bank.

I was speculating on whether this new plan would follow the same route,
after all there are abandoned platforms at Charing Cross
and some tunnel east of there towards Aldwych. There is also some protection
of the route, and some construction at City Thameslink.

Peter.