Even an air rights scheme needs to take account of future needs at platform
level. Unless there is intention to use skyhooks technology someone needs to
decide where to put the columns which will hold the buildings up.
I thought one option for Crossrail 2 was to run Wimbledon - East Putney -
Wandsworth Town - Clapham Junction before tunnelling to Chelsea and on to
Hackney, and I hadn't heard that this option had been abandoned.
Crossrail 2 seems to have been abandoned as a crossrail type of
connection; if it had gone ahead as a crossrail thing it would have
been clapham junction-victoria-kings cross-dalston junction,
without any other stops.

But the chelsea-hackney ("chelnea") tube line still seems to be
regarded as planned to go ahead once the funding arrives. There were
three alternative routes being suggested; all the routes go from
Wimbledon to Victoria (and then off to the central line beyond
Leytonstone via Angel, Dalston, and the Hackney Marshes), but they
differ in how they go from wimbledon to victoria.

All three routes go from East Putney to Wimbledon. From East Putney to
Victoria the three options a
-(right angle) via Parsons Green, Kings Road (Chelsea), and Sloane
Square
-(straight line) via Clapham Junction and Battersea Park (East)
-(S bend) via Clapham Junction, Battersea (West), Kings Road
(Chelsea), and Sloane Square

the first of these (right angle) was the original option, but the last
of these (the S bend) is the one preferred by Kensington & Chelsea
council