[steam for ever]

I suggest that 3 car 172s with corridor ends like those delivered to London Midland would suit Northern the Best. I think that for the majority of services they have outgrown 2 car trains. To leave room for growth on intercity routes perhaps 4 car train would do the job.
Maybe now if they got their licence to run loco hauled trains they could use the stock that Wrexham and Shropshire used.