Where do you propose getting train crew from for this?
I don't know how long it would take to find rotas that worked, was hoping it might be possible from the summer when the Cambrian needs its 158s back. I appreciate staffing is tight but I do not think it needs that many to run an additional train from Manchester to Crewe. Maybe it does, and if the overtime ban continues then I can see that it is impossible.
It feels like the situation at the moment is one of finding reasons why things cannot be done and it does not matter what sort of company is running the trains. When Arriva were kicked off everything was about how great TfW would be but my experience has been anything but.
I would still look seriously at Crewe to terminate the Manchester trains until there are enough units available to run more than a single 150 on the Marches. Knowing that you have to be at Piccadilly for the xx06 Northern to Crewe is absolutely fine, because presently to catch the xx30 you have to be at Piccadilly in time for the inward working.
It might help to stop selling advance tickets for the change at Crewe onto London trains, that surely can be changed to the Northern services for ticket acceptance between Manchester and Crewe.
Its coming to something when waiting at Piccadilly the 4 car Northerns on Buxton/Chester runs inspire jealousy.