I don't think that there's any need to overcomplicate Liverpool-Scotland services with portion working and other exotic ideas, but it would be handy to have them serving both Edinburgh and Glasgow alternately in the same way as the Manchester Airports do at the moment. Knowing how many people change at the moment, and how busy the Scottish TPEs are generally, my guess is that Glasgow and Edinburgh would see similar loadings from Liverpool. I'd happily build my travel plans around a relatively infrequent direct service, although anything less than a train every three hours wouldn't be enough.
I agree about some of the over-complicated "solutions" being suggested on here.
Instead of the various coupling/uncoupling ideas, one idea not suggested so far would be to reverse the Edinburgh - Carlisle (Manchester/ Birmingham) services at Carstairs, and stop all Glasgow - Carlisle (Manchester/ Birmingham) services there too.
It'd take an extra couple of minutes on the Edinburgh services, but (combined with stopping the Scortail/XC services from Glasgow Central to Waverley at Carstairs) it'd hopefully give connections at Carstairs for Glasgow/ Edinburgh - meaning that passenger numbers would even out more (i.e. no need for Edinburgh-bound passengers to wait for the next Edinburgh service at Preston - they could jump on any northbound (ex Manchester/ Birmingham) service.
(I'm not talking about the complicated joining/splitting at Carstairs that they used to have in the '80s, I'm not trying to run any additional services, I accept it'd be a massive over-provision for Carstairs passengers, but you could provide a lot more connections for Scottish passengers by offering regular opportunities to change there)
What a wonderful flexible forward-looking customer-responsive railway we have (not!) It's a good job that only 10 class 350 units isn't set in stone forever. Anyone still care to defend the current privatisation/stock ownership structure?
Manchester - Scotland?
I remember the irregular service in BR days, run by 158s (or even two coach HSTs!).
This became a clock face bi-hourly service at Operation Princess, with brand new four/five coach trains (running through from the Thames Valley and West Midlands).
This was replaced by a dedicated service from Manchester Airport to Scotland (i.e. not already full of Birmingham passengers), modern three coach 185s, slowly upgraded from bi-hourly to 3tp2h.
This was replaced by brand new trains (10x four coach 350/4s - able to run 110mph) running every hour.
These are being replaced by another fleet of brand new trains, a dozen five coach 125mph 397s (with the option for more units to be built), with the hourly Manchester service supplemented by some Liverpool - Glasgow services.
(this is at the same time as Euston - WCML - Glasgow was doubled in frequency to hourly, and Birmingham - WCML - Scotland doubled to hourly, so not as if the Manchester services are at the expense of something else)
Is the current privatisation/stock ownership structure absolutely perfect? No. But it seems fairly flexible forward-looking and customer-responsive for passengers between Manchester and Scotland - they've seen a lot of improvements since the BR days - they are almost ready for their third brand new fleet in under twenty years. Maybe in another five years there'll be another (bigger, better, faster) new fleet on the way?
The fact that some people are complaining that a five coach train every hour from Manchester (on top of the ex-Euston/ Birmingham/ Liverpool services to Scotland) might not be enough shows that improving the trains every few years increases the demand for those trains - it's a virtuous circle - it's something we should be celebrating.