You seem to be misunderstanding my comments, or we are in agreement. I said [re the Manchester station] "the services from the south are[n't, sorry] going to fill the lines to capacity are they?" so my comment that the new through platforms at Picadilly should be able to provide the capacity to take NPR services too was spot on. I also meant that the platforms (or the trains) could be built so that both could safely call. I don't think these contradict each other at all.
To B&I I would say why on earth should NPR services terminate in Manchester? Surely the idea is to have a coast to coast trunk route and leave the terminal platforms at Manchester for local terminators.
By terminating platforms at Manchester, I meant in the new station for HS2 services. Although the distortions being forced on the route by the set-in-stone approach to HS2's Manchester end might make you think otherwise, there would be little point to an NPR that does not run through. Had someone done something to get local terminators out of Piccadilly, remodelled platforms extending from the existing shed might have been sufficient.