So building on this, given this is speculative discussion, what do we all think could be a sensible WCML/HS2 service pattern, based on the following hypothetical constraints -
OOC terminus till mid 2030s; it can cope with 6 2x200m (400m) trains off peak but with a peak flexing up to 8tph.
Handsacre built via the fast lines - so capacity for around 6/7 HS2 trains.
Crewe has 2 400m platforms where trains can split / join. Carlisle also has platforms lengthened to 400m.
Rolling stock remains at 200m, but units reconfigured to seat 600; matching an 11 car pendolino.
My own view is that perhaps controversially, Birmingham doesn't need 3TPH HS2 trains, but that 2 400m trains an hour via HS2 would suffice and still provide a huge capacity uplift - 2400 seats/hour vs around 1800 seats today (if 3tph, which often isn't the case). Therefore, you could look at for the Off Peak services -
2TPH 400m OOC-Interchange-Curzon St.
3TPH 2x200m OOC to Crewe, with the front 200m unit going to Manchester via Stockport (1tph Wilmslow) - providing a 3tph train to Manchester. The rear 200m units provide a 2tph service to Liverpool and 1tph service to Preston. This gives Liverpool a 20/40 minute service interval; not ideal but still an improvement on 1tph now.
1TPH 2x200m OOC to Carlisle with the front 200m unit carrying on to Glasgow.
On the classic line, 1TPH Pendolino goes Piccadilly to Euston via Stockport, Macclesfield and Stoke.
I'm not a planner, so this is pure speculation - feel free to shoot this down