Peter Masson wrote:

But how about Barking -
Gospel Oak (would need rebuilding so that through trains could call)
- Willesden Junction - Ealing Broadway - Greenford.

Gospel Oak is one of the worst sited stations in London - its catchment area
is a quarter parkland and a quarter cut off by other railways. Building
platforms at Tufnell Park (with entrances at both ends of Churchill Road)
and running the Greblin through Gospel Oak without stopping must have a
better cost-benefit ratio.

IMHO curtailing the Ealing Greenford line to a shuttle from West
Ealing will be a considerable disbenefit - passengers for the LUL
District Line will have to change twice at West Ealing and Ealing
Broadway, though passengers for the Central Line will be able to
circulate the other way via Greenford.

But the curtailment must surely be to make capacity for other trains between
West Ealing and Ealing Broadway, and your plan doesn't address that.