I think we're under-estimating, especially for their sizes, how many commute from Todmorden and Hebden Bridge (and some others) to both Manchester and Leeds. They both need 2tph of reasonable speed to each. More so than Rochdale I would say, but I like it as an intermediate hub and place to pass. More lines there could help.
Yes the Calder is secondary to the main Huddersfield route, but it links a lot of decent sized places and a lot of 'above their weight' commuter locations. If it was ever electrified, sped up and more frequent, I think slow and semi usage would eclipse Standege, which is more weighted to fast services. So it has a role for sure.
If the Blackpool service remains via Bradford - which I agree with, it's a long-standing connection and a rare 'long distance' service for the city - then could a second service, for example from Preston, run to Hull via Brighouse? Or even Manchester - Halifax - Dewsbury - Hull. For the pairs, not the end-to-end. The current one doesn't quite do as much.
Westwards, I agree that Chester should be the fastest pattern, for Chester-Leeds services (Warrington too). A second fast pattern, rather than Wigan - might be able to be joined up with the other North Wales service (Llandudno, to be Bangor) to provide some consistency on that corridor. And remove a Piccadilly. Plus more longer distance possibilities for North Wales.