On that basis, you could say the same about any of the services through West Yorkshire. Any one of the other Calder Valley via Bradford services could fulfill that role just as well, but for some reason it is always the Blackpool that gets mooted.
To be honest it's York that's the problem anyway. I wouldn't advocate completely axing the through Trans-Pennine service to Scarborough, but the York to Scarborough section is noticeably more reliable when it runs as a simple shuttle. If ever the proposed second hourly service on the route materialises I'd definitely advocate that service operating as a shuttle from the bay platform at York.
I would suggest that the optimum service for the Scarborough branch is:
1tph Scarborough - York platform 2
1tph Scarborough - Leeds and beyond
One service gives connectivity and the other reliability.
I thought that supposed issue with 170s had been, if not outright debunked, at least quashed somewhat by people "in the know"?
In any case even if they're damagingly inefficient at lower speeds, they're no worse than running 185s on routes they aren't suitable for due to their weight.
The issues of 170s on the Harrogate line are two-fold. Reliability has been significantly improved by Northern gaining knowledge of the units, but also by cycling them through Sheffield - Scarborough; fuel economy is as bad as ever on the Harrogate line.
Coming back to the original thread title, and remembering we are in the Speculative discussion sub forum, I would suggest that the 3rd Hope Valley express should be a TPE service from Manchester Piccadilly to Lincoln service calling at New Mills Central and Dore. The resulting services would be:
1tph Manchester Picccadilly - Lincoln (New Mills Central, Dore, Sheffield, Worksop, Retford, Gainsborough Lea Road, Saxilby, Lincoln)
1tph Sheffield - Gainsborough Central (reinstate the pre covid service)
2tph Leeds - Nottingham (the current Northern Leeds - Lincoln becomes a second Nottingham per hour)
This reinstates 2tph on the Lincoln route, gives Lincoln a service to Manchester, doubles one of Northern's busiest routes (Leeds-Nottingham) and at the loss of Leeds - Lincoln, which lets face it, is much quicker via Doncaster, so really the loss is Barnsley and Meadowhall to stations on the Lincoln line, which yes is a loss, but I would argue is significantly outweighed by the gain on the other routes.