I thought Inverness was the fastest growing place in Scotland?
Regardless, proximity to the capital is more important - Dunfermline and Stirling are in the prime commuter distance from Edinburgh and much deserving of the increased service (by my reckoning Aberdeen would get around twenty coaches an hour to Edinburgh under your plans).
But even if you do find spare HSTs to give Aberdeen up to three trains an hour to Edinburgh, why extend them to Leeds (creating delay exposure elsewhere)? And why not use any spare HSTs on beefing up the XC core, or (if they are run by EC, on Lincoln services etc)?
Why?
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But Waverley125 keeps telling us that its faster to go to Manchester/ Birmingham down the WCML (and wants to cut the Edinburgh - ECML - Birmingham link)?
No, both economically and in terms of population it's Aberdeen.
As for what Aberdeen is getting, in terms of it being one 9-coach HST per hour, one 9-coach HST every other hour (i.e. 4.5 ph) and some form of DMU (two 170s?) per hour, it probably works out at about 20, yes.
I would also support Stirling and Dunfermline getting more services, the two are not mutually exclusive in any way.
As for 'why Leeds', because it's the UK's 4th biggest city, and besides being a destination in its own right (as you agree when you say XC should serve it), terminating at Leeds
reduces delay exposure by reducing the distance the service travels and its potential to cause conflict.
You then don't need the HSTs, as you can use the spare Voyagers to beef up the XC core (fwiw I'd also support cutting XC services in the southwest back to Plymouth). This means you can double up more services and provide a higher frequency, so all-round win for the midlands.
And yes, it's much faster to go down the WCML-so an hourly 350 on Manchester-Edinburgh & Manchester Glasgow, and an hourly Pendolino on Birmingham-Glasgow & Birmingham-Edinburgh, means you increase capacity down there and can actually speed up London-Glasgow trains as, post-Blackpool wiring (I'm assuming an hourly Blackpool-London train) all Euston-Glasgow services can be first stop Preston.
Altogether, I think it's much better to run overlapping service patterns for specific areas rather than run one long service, as you get more efficient use of units, and create higher frequencies along the 'core' sections, while preserving the fast calling patterns in the extremities.
Another example would be Penzance, e.g.
1tph Penzance-Paddington (semi fast to Plymouth, Newton Abbot, Exeter, Paddington)
1tph Penzance-Plymouth (all stops)
1tph Penzance-Bristol (semi fast to Plymouth, Totnes, Newton Abbot, Teignmouth, Exeter, Taunton, Weston super Mare)