As EMR are going to be short on units and quite possibly are going to have to retain some of the 158s the obvious solution would be to swap the 158s for more 170s, either from Northern, TFW or Scotrail. Take Northern for example, they have 16 170/4s and EMR have 26 158s, you could swap these giving Northern the whole 26 to compensate given that the 170s are 3cars and then both EMR and Northern would not be operating a microfleet of different units. There would be no extra staff training as both would already operate the type and would make it easier on diagramming and maintenance aswell. But we all know the railway doesn’t do this type of joined up thinking.