Going off my rough working to cover the busiest Blackpool-MIA/Hazel Groves would need 6 double sets so 12x3 car 331 with 3x 4car 311s to cover the others, along with 7x 4car 331s to cover Liverpool-Blackpool/Wigan. So 10x4 and 12x3 in service with likely total of 12x4 and 15x3 in the west which I’m assuming is at least doable although things may get tight when the 319s go and another 2 units are needed to cover Preston-Victoria if 323 training isn’t complete at that point.
Long term if there’s a wish to sub double 323s on some diagrams going off the sectional appendix the problem platforms are;
Layton Up 98m (140m)
Salwick Up 93m Down 93m
Leyland 1-3 101m (120m) 4 100m
Adlington Up 127m Down 124m
Blackrod Up 114m (140m) Down 114m
Davenport Both 138m (140m)
Woodsmoor Both 90m
Gatley Up 106m Down 122m
East Didsbury Up 104m Down 112m
Mauldeth Road Up 121m
Focusing on the Blackpool- Hazel Grove drops the requirement for platform extensions to Leyland, Adlington, Blackrod and Woodsmoor. Allowing up to 4 of the 5 diagrams to be run by 323s (one starts in Stoke and still need ASDO) in turn allowing all Blackpool-airports to be 6 cars or all Liverpool- Blackpool depending on demand, freeing 4x 4car 331s for use on Hadfield services.
West EMU use would be roughly;
331s
Blackpool Hazel Grove 8x3 1x4
Blackpool Man Airport 4x3 2x4
Blackpool Liverpool 3x4
Wigan Liverpool 4x4
Total 12x3 10x4 [15x3][12x4]
323s
10 Liverpool-Crewe-Piccadilly-Crewe-Liverpool-Warington
3 Hadfield
3 Stoke
1 peak Liverpool-Man Vic
1 peak Stoke
2 Preston-Victoria
+2 for lazy counting
22 [34]
with extras
3 Man-Macclesfield
1 extention to Stalybridge
+1 other
27 [34]
And after platform extensions;
331s
Blackpool Hazel Grove 4x3
Blackpool Man Airport 8x3
Blackpool Liverpool 3x4
Wigan Liverpool 4x4
Hadfield 3x4
Total 12x3 10x4 [15x3][12x4]
323s
10 Liverpool-Crewe-Piccadilly-Crewe-Liverpool-Warington
6 Blackpool Hazel Grove
3 Stoke
3 Preston-Stalybridge
3 Man-Macclesfield
1 peak Liverpool-Man Vic
1 peak Stoke
+3 for lazy counting/other
30 [34]
If passenger numbers do recover I think to long term issue may actually be a lack of 4 car 331s which a lot routes getting single 323s already could have done with pre-pandemic.