It would be the obvious choice (for NPR at least) if it weren't for the following:
1. Victoria lacks connectivity to the densely populated areas of South Manchester (SM)
Whilst Victoria is most definitely the best station to access the city centre, it is the worst for onward-connections by rail. It has decent connectivity to North Manchester (NM) and its respective towns i.e Rochdale, Bury, Oldham etc. To connect SM we could say "let's run metro frequency services over the Ordsall Chord" Okay, that makes sense on paper, but practically to do that we're going to have to:
A: Have to find terminating capacity at/beyond Victoria
B: Sacrifice services from Piccadilly via Bolton/Wigan etc.
C: To run such high frequencies reliably, we're going to have to lock Castlefield to the Styal Line to minimise conflicts on the Piccadilly throat. That means we're only really connecting people on that line, requiring yet another change at Piccadilly for onward-travel to the rest of SM.
2. Site Contraints & Accessibility
The platforms are long enough to accommodate the 200m sets proposed for NPR, but the station itself has an incredibly inefficient layout, with cramped walkways, poor accessibility (the stairs have to navigate around the arena supports making escalators a no-go) and a concourse with very limited space for shopping and hospitality amenities that a major intercity station would require. There's Alsop the issue of getting to the Metrolink platforms that require at-grade crossings. This just about works today with the footfall the station receives, but double that and there's going to be some serious crowd flow and safety issues. Piccadilly on the other hand has (due to be moved and expanded) Metrolink platforms in the undercroft with much better accessibility and crowd flow. Also, as much as I think we all dislike the Arena dominating the station preventing development and making the platforms dark etc. It's not going anywhere. It's a major asset to the city in terms of drawing in leisure travellers.
3. Political Reasons
There's a huge (not to be underestimated) political drive to serve Manchester Airport with NPR. TfN and the IRP both propose utilising HS2 infrastructure to get NPR services through Manchester. Whilst many of us (myself included) think this is a flawed idea (as it limits NPR services to 6tph with no room for future HS2 services, and passengers value frequency over direct connectivity, see Crossrail) there is a lot of support behind it. It might be a reasonable compromise to go via Piccadilly assuming we have metro frequencies to the airport, but from Victoria we're adding an extra 15mins to a 21min journey. That's not going to go down well with politicians who are already peeved about losing a direct, express airport service.
Manchester's network is a tough nut to crack, due to it's highly constrained nature with flat junctions and narrow viaducts making large infrastructure interventions on existing lines difficult to implement. The optimal solution of course, would be to serve both the NM & SM markets with two NPR stations via a tunnel/s. Victoria might first spring mind as an ideal location for a second station, but it would have to be a mined station with limited space to integrate it and manage crow flow, as well as being prohibitively expensive. The route that tunnel would take would be circuitous facing the wrong way at Piccadilly (unless using HS2) Another way of doing it is to put a second station in Salford west of Oldfield Rd. where the lines from both NM & SM "bunch up" That area has space for a shallow-box, possibly open-air station, providing an excellent interchange between intercity services and commuter services to NM. We could even lock the Bolton Corridor to the Rochdale Corridor then, taking out conflict points around Ordeal, as there would be a good level of connectivity for NM residents without having to traverse Castlefield to reach Piccadilly.
It also opens up space for more services over the Ordsall chord which, along with the rest of the existing network, would become able to operate as an "S-Bahn" style network, with metro-frequency services to destinations outside GM and separating out ALL intercity from commuter traffic (assuming a new/upgraded line from Salford to Liverpool with a junction toward Warrington, and Lancashire/Scotland. Assuming a portal near Ashbury's, we can bring in service to Sheffield too, taking those of the Castlefield Corridor and boosting the case for new underground infrastructure through Manchester in the form of a 2.5mi tunnel. With new/upgraded lines either side of the city, it could see 8-12tph depending on timetabling options and allowing for adequate dwell-times. That's much higher capacity than running via HS2 which is limited to 6tph.
The question raised is a very good one, as it does seem logical to go via Victoria at first glance, but once we go deeper it becomes clear it's not really a viable option, and arguable neither is running via HS2, especially if NPR is to use TRU (which is looking more and more likely) making timetabling NPR trains onto HS2 reliably a very difficult challenge, potentially building-in problems from day one.
Just my thoughts on it!
George.