As has already been discussed on the
Northern Franchise Awarded to Arriva thread, getting trains from one side of Manchester to the Other is surprisingly difficult, due to the nature of where the suburban services run. Hazel Grove to Preston will run, I believe as a 2tph service already, but the Hadfield service certainly won't.
Anything that's going to be running via the "through" platforms at Piccadilly will be going either to the Airport or via Stockport (even then, the Stockport services do still eat up paths across the Piccadilly throat), hence why Stalybridge - Victoria is being wired up, to reduce Victoria terminators from the West of Manchester. "Suburban(ish)" services (post 2019) are:
West
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2tph from Newton-le-Willows (Electric)
2tph from Warrington (Diesel)
1tph from Kirkby (Diesel)
2tph from Southport (Diesel)
2tph from Preston (Electric)
2tph from Blackburn (Diesel)
3tph from Wigan (Diesel)
East
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2tph from Hadfield (Electric)
2tph from Rose Hill (Diesel)
2tph from New Mills (Diesel)
2tph from Hazel Grove (1 Electric, 1 Diesel)
2tph from Stalybridge (Electric)
2tph from Rochdale (Diesel)
2tph from Alderley Edge (Electric)
2tph from Macclesfield (Electric)
2tph from Crewe (Electric)
2tph from Altrincham (Diesel)
2tph from Airport (Electric)
Without having significant Diesel under the Wires, you need to match up electric services with electric services. Additionally, due to the inability to interchange without going all the way into Manchester and out again, you need a decent service from each branch to each "line" (Oxford Road Corridor and Victoria).
Linking these up, you're probably looking at
Blackburn - Rochdale (2tph - Diesel)
Newton-le-Willows - Stalybridge (1tph - Electric)
Newton-le-Willows - Airport (1tph - Electric)
Warrington - Stalybridge (1tph - Diesel)
Warrington - Airport (1tph - Diesel)
Preston - Hazel Grove (1tph Electric, 1tph Diesel to Buxton)
Kirkby/Southport/Wigan - Victoria (6tph Diesel)
Alderley Edge/Macclesfield/Crewe/Altrincham/Hadfield/NewMills/Rose Hill - Picc (14tph - Mixture)