This is not London, this is part of the Northern Powercut, it has to be cheap.
On a practical level, I don't think it would work, the branch to Salford goes under the Metrolink, a double deck line wouldn't get under it. It would be a lot cheaper to make it 4-lines all the way; but there would then be a lot of demolition.
Not as much demolition as you'd think if you're willing to build an open viaduct over the road, and run back to 2 track from Oxford Road to Piccadilly.
The questionable part is just where do you cross over between the stations.
I'd look at changing between paired by route and paired by direction between Deansgate and Oxford Road, then you have two sets of slotting to do in two places rather than one.
To summarise.
4 track from Ordstall Lane Jcns, with a double slip crossover to get from the Liverpool Lines and Windsor Link before the CLC lines join (or alternatively have the Windsor Link maintain line of seperate route and be crossed by the Vic - Warrington route so it comes in as a natural 4 track, the chord joining in with the Windsor Link Lines)
Either way, we have a four track formation at Deansgate, four platforms from South to North being...
W/B CLC, Newton and Windsor Link
E/B CLC, Newton and Windsor Link
W/B Windsor Link and Chord
E/B Windsor Link and Chord
The E/B CLC, Newton and Windsor would need to cross the W/B Windsor Link and Chord between Deansgate and Oxford Road to then move to having two E/B and two W/B platforms at Oxford Road, with the possibility of terminating trains on platforms 2 and 3 if required.
These trains would then be held in their E/B platforms until clear in an alternate platform working, as with Piccadilly, the same would apply in reverse, trains being held until they're ready to complete the crossing moves, this would help build a lot of resilience back into the timetable.
I know this is hard to follow my brain, if anyone is actually that bothered about this, and how it could tie in to a possible re-opening of Manchester Central as a railway station, I'll do a schematic upon request.
Cheers all
