The top end of this lift isn't accessible to the public
At the moment... Hence why it would be a good idea for them to close
the passage from ticket hall to GNER and turn it into a slope down,
going from airside ticket hall, to one floor below the ticket hall
level at the top end of this lift.
I'm not that sure they are trying to alter the layout, at this stage.
What layout would that be? The GNER-to-tube passage is being filled in
anyway, as they will be demolishing the 70s concourse, and its layout
was always up for alteration.

I'll have to guess where
the Victoria Line lift goes, is it directly ahead as you arrive from the
Piccadilly, or when you arrive from the old KX Thameslink stations, or
in between; and north or south of the passage parallel to the platforms?

* * * * * * * * * * *|
* * * *=============================
* * * * * * * * * * *| 3 4
* * * * * * * ssss----------sssstairs
* * * * * * * * * * *1 2 |
* * * *=============================
* * * * * * * * * * * * *|

ie at site 1,2,3,or 4?
I'm not exactly sure what your diagram represents, as the passage
south of the victoria line should join up with the passage north of
it. But essentially, the lift is being added in the position you've
written "ssss" on the left hand side of the "----"

A more accurate diagram for the victoria line would look like
|
=============================
|
Lift | stairs
|
=============================
|