In "Box Modeling", the method is to pushpull a face (without it creating an internal face in other modelers), then scale the new edges as desired. Then pushpull again and again, scale some edges. Then pushpull and do this over and over. Dozens, hundreds of times very rapidly. Until you have a boxy pproximation of a curvy shape (like a plane or space ship). Then once you have all the boxed made, you subdivide and smooth.
So it is a very fast, repetitive process of pushpulling. having to delete each internal face is a major showstopper for this modeling method. This project is still on my mind. I am working on some groundbreaking UI stuff (well, sort of groundbreaking - someone else already beat me to the punch, but it might still be cool). Once I work out some stuff, this plugin might well be one I release in the next few weeks.
Chris