... or Rochdale </watchthisspace>
Or both...
Remember what we're potentially looking at coming in from the West is anything up to:
4tph from Bolton, possibly 5 or 6tph if capacity is constrained through Oxford Road, unless we do some major re sculpting of the timetables through Bolton, hacking off Westhauton from direct services to Manchester, changing from running 2/4 car units to running 6/8 car units less often, requiring SDO or UDS for Salford Crescent.
2tph or 3tph from Atherton.
So this could be up to 9 or 10tph in the peak from Windsor Bridge, and roughly 6 or 7tph off peak.
Ordsall Lane is less relevant to the capacity constraints at Victoria as there is a lot more space to put in platforms to terminate services from here, there is also space for a degree of grade separation at Ordstall Lane to take terminating services from Eccles over the top to land able to terminate where Exchange used to be, moving walkways can take pax to these platforms, and through services (at roughly 6 or 7tph). (4tph to Leeds (2 Cord, 2 Liverpool), 2tph Calder Valley (Cord), 1tph Liverpool - Norwich)
With anything up to 5 or 6tph terminating from the direction of Eccles, (2tph Wigan, 2tph Liverpool, 1/2tph Chester via Warrington BQ). In my opinion, all of this together is too much for the four through platforms to take on their own, both in terms of passenger flow and on track capacity, and grade seperation at Ordsall Lane will need to come at some point, with 16tph per direction all using the same flat junction, with even more if you include Castlefeild Junction, adding G/S from Eccles to Victoria alters this to a basic four route merge, without any crossing traffic (CLC, Chat Moss, Windsor Bridge and Cord) since a Vic to Chat Moss service would need to cross, every, single, line, the issue currently crippling Piccadilly.
So; my personal solution that I can see to this would be:
Add in some bay platforms during CP5 or early CP6 to Victoria on the former Exchange site, 3 or 4 bay platforms.
Grade separate Ordsall Lane during the Cord works, creating a 6 track approach, an S shaped viaduct from the unused trackbed section on the Deal St - Ordsall Lane viaduct, carrying everything over the top, cord traffic will use the current tracks. The 6 tracks would all of course be bi-di etc, but assigned usage in this basic order at Deal St: (North to South) Windsor Bridge Lines, Ordsall Cord Lines, Eccles Lines, working into platfoms 5 and 6 for Windsor Lines, 3 and 4 for Cord services, and new platforms (7, 8 & 9) for terminating services, attempting to seperate everything out on the Western side of Vic.
Bay platform(s) at Rochdale added back in to push Diesel services via Windsor Bridge through to (it's on the right side of the tracks) Rochdale. Likely to be 2tph from Blackburn (Aspiration) and 2tph from Wigan via Atherton. Also including anything else you care to push through Bolton or Atherton, 4tph would actually be enough to run the Calder Valley services, but the fast services across the Calder Valley are to be extended to Chester or Airport last I checked, leaving two spare, but providing 6tph to Rochdale.
Using the Stalybridge platforms provided for EMU services from Bolton, likely to be 3 or 4tph.
Re-write the timetables West of Bolton, through services to Wigan via Bolton are nice, but are not imperative off peak. If Lostock to Wallgate becomes electrified before the cord is implemented, then it would retain through services, at 2tph EMU, with 2tph EMU from Preston in addition to this.
I think you can guess the rest of the timetable, and I need coffee, so I'll leave you with that...
EDIT:
If we're seeing a lot more services it would potentially be worth re-building Ashton Under Lyne and putting in four track from Vic to Stalybridge, 2 for the bays and 2 for through. Would probably be able to see 8tph EMU pushed through then, or some DMUs scattered in the mix too.