To the south would be so far away from the other exits and entrances
that it would be ridiculous connecting to it,
Wouldn't it be as close to the 1960s ticket hall as the Victoria platforms
are, and right under the Circle platforms? It would also be in roughly the
right place to inherit the KX Thameslink exit onto Pentonville Road, no?
If it was right under the circle platforms, then it would probably be
in the same place as the victoria line running tunnels just before the
platforms. It would have to either be further south, or very very
deep, either way making escalator access very awkward.
KX Thameslink is far to the south east of the other platforms;
anything in the right place for that wouldn't be very convenient for
anything else, unless (again) it was very very deep, so that
escalators at either end could stretch far enough to reach the rest of
the tube platforms as well as KX thameslink.