On the normal cube the relative positions of the faces
is immutable, however this is not so on the 4x4x4.
I have found a trransformation which i beleive will facilitate
the switching of any two of the cental blocks of 4 on a face.
I am not sure as I did this totally in my head, without
the benifit of a 4x4x4. This trandsformation would be
extremelly nasty to pull on someone who has learned how to
solve the standard cube from someone else, and as such does
not know much about cubolgy.