Ordering 2 and 3 coach trains instead of 3 and 4 gives greater flexibility for doubled-up working, because of platform lengths
They should have ordered them with corridor connections then.
the May 2018 timetable shambles was not the fault of Northern - they simply had to fit around new TPE services, the new poorly thought out infrastructure and their own franchise requirements, which inevitably led to delays and cancellations
I agree that, if NR had provided these paths to Northern then it's not entirely Northern's fault if they cannot run them - this isn't like a bus company introducing a new route without taking traffic congestion into account - if the paths were not reliable then they shouldn't have been granted.
But then, the paths are a mess. I don't know how much of the problem is down to Northern and how much down to the franchise requirements but the muddle of routes and the complicated interworking has been a disaster.
Mainly this is a "west side" problem. Yorkshire diagrams seem simpler than in the days of Abellio/Serco (remember the "Grand Tour" from Manchester to Wakefield via Selby, and the Sunthorpe to Adwick via Lincoln services?). Yorkshire has a number of "shuttles" which terminate in Leeds/ Sheffield (which keeps thing simple). But the "Lancashire" ones are a mess - Liverpool to Crewe via Oxford Road being one obvious example. Things could be a lot simpler but the desire for all of these cross-Manchester links means that if one bit of the network fails then everything else gets affected.
But is that Arriva's fault, or the fault of a franchise where the "Stakeholders" had a long list of through services that they wanted like Bradford to Liverpool/ Chester/ Manchester Airport (instead of a simple Calder Valley service which could have longer trains at a sensible frequency, instead of a lopsided timetable with big gaps in simple journeys like Halifax to Bradford)?
I know that the Liverpool/ Manchester Airport services haven't happened yet, of course, but that's an indication of the complicated franchise demands that anyone would inherit. Replacing Arriva wouldn't resolve things - it'd just give the job to another organisation who had to deal with squabbling "Stakeholders" each with their own unrealistic demands about how important their local station/line was.
Of course, this also occurs at London commuter TOCs - Northern are not the only one experiencing poor service for exactly the same reasons at the moment! Of course any "race to the bottom" (choose the cheapest) franchising system will always lead to this, because companies will make undeliverable bids as they have to to win.
In fairness, more of the recent franchise awards seem to have gone for an element of "quality", rather than the lowest subsidy (or highest premium) - this seems less of an issue nowadays than it used to be.