I was thinking more of the current situation, where all Scarborough services apart from 2 late evening ones are York shuttles. It would be more useful if they connected at York with the Airport service rather than Liverpool ones as this adds 30mins to Piccadilly and Airport journeys, which I would have thought have more passenger flow than Liverpool
Looking at a post Covid situation I would support undoing May 2018 as:
- Journey times are now slower particularly where onwards connections have to be made at Piccadilly
- Service is less reliable when a full timetable runs
- Destinations served are less useful
- Castlefield is always going to be a bottleneck, removing the airport trains from it will help
- Merging the stopping services west of Huddersfield into the Hull service has proved unpopular with Hull/Selby passengers (trust me on that, a few family members from Hull used to travel to Manchester by train, but the deterioration in service means they have abandonded the railway, to be fair its not just about the extra stops and resulting overcrowding, and it was pre covid but thats another discussion)
The (white) elephant in the room is then the Ordsal Chord, in a ideal world extend the Airport stoppers to Man Vic, instead of running long distance services around it, but there are no west facing bays at Man Vic. I will probably get shouted down, but IMO it was a waste of money unless the other improvments you mention are delivered, and the money would have been better spent creating some additional passing opportunities between York and Manchester, some easy ones would be Crossgates, Slaithwaite and the Western end of the Stanedge tunnel where there is already a freight loop east bound.