Adrian Auer-Hudson wrote:

Operationally converting the [Greenford] branch to be a Central
Line extension makes sense. The question is: Would the
construction costs be justified?

And which end do you connect it at?

Though a loop at both ends has its attractions from an aesthetic point
of view!

If tube tunnels were dug between West Ealing and just east of Ealing
Broadway, it would free up surface capacity at Ealing Broadway station
for the desperately-needed rebuilding.

There are endless options, and I think a wholesale reorganisation of
services might be beneficial, because
- the area needs north-south rail services
- the line parallel to the Central line is ridiculously under-used
- passengers beyond Northolt are not best served by an all-stations
service
- The Ealing Broadway Central Line branch will lose most of its
passengers to Crossrail

I'm thinking maybe a much enhanced Chiltern service from the Ruislips,
and new Central Line branches closer in: West Ealing via Castlebar
Park, and maybe something heading north into Park Royal.

Colin McKenzie