People seem to love Nottingham to Glasgow, which seems arbitrary but I guess it takes in Sheffield too, so would connect 3 decent sized cities to Glasgow. Even starting at Sheffield might be interesting - but still requires a reversal at Leeds.
The issue is simply that the line passes through a lot of sparse country. And even Carlisle isn't that big a destination, and it's 100 miles north to Glasgow. Edinburgh would never be worthwhile vs the ECML.
Agreed.
Leeds - Glasgow is currently just over four hours on XC - the service runs bi-hourly.
Leeds - Carlisle is currently around two and a half hours, and you'd need to add over an hour to get up to Glasgow (but that's basing the WCML section on diagrams pathed for a 125mph tilting train, rather than trying to find a path for a Sprinter like Northern Spirit used to).
So even if there were paths on the WCML for a Sprinter, or we found a few spare 125mph DMUs down the back of the sofa (and decided that it'd be a good idea to use them to spend most of their time trundling along the S&C at half their top speed) then it's not going to be much faster than running via Edinburgh...
...and you'd be running a service that has intermediate stops at Skipton/ Settle/ Carlisle rather than York/ Darlington/ Durham/ Newcastle/ Edinburgh...
...so there's not much of a time saving for inter-city journeys and you'd be serving relatively smaller places... it seems a pretty thin business case.
Whereas, one Voyager is all you'd need to increase the Leeds - Glasgow service to hourly during the daytime (i.e. extend the current XC services that terminate in Edinburgh).
(this is all assuming that there's spare paths from Leeds to Skipton, given that the line is already so busy that 331s are being built to permit six coach EMUs to run, and two stations have been built on the line from Leeds to Shipley in recent years)
Feels like, if the S&C had closed in the '80s, it'd be a great cause celebre now, enthusiasts suggesting this amazing future for it, if only we'd re-open it - just think of the untapped demand etc. Whereas, it stayed in operation and (despite record passenger numbers on most lines in the UK) is still just a Sprinter every couple of hours with unremarkable passenger numbers at stations north of Skipton (despite the Leeds commuter market having changed considerably over the past generation). A bit like a rockstar who turned out to be a racist middle aged nonentity, rather than being remembered as a talented hero who died in the "27 club".