Oh hey im sorry, I was just putting my two cents in on the density of Poser meshes :)

Fred and Haloedrain are correct I think, using a lattice would be the way to go if you were changing the shape of a model as dense as V3 or Aiko. 
Another good way is using proportional editing combined with the 3d transform manipulator (the little hand) set on Normal.

Your dress model looks really good by the way, nice touch on the wrinkles in the shoulder.

While I'm here, a word on fls13's statement. That method is they way it all used to be done I think. But now, as the technology progresses, we can have things like dynamic cloth, softbodies, and other tools to make the models and clothing look and act even more realistic. So having a body underneath really is a requirement for realistic renderings and animations.