Why do all this import & export stuff? If you're going to have your characters in a scene, put your hair and clothes on your first character, then add him/her to your character library. Then do your next character, add him'her to the character library... Then when you're ready, place your scene first. Then add each each individual character from your character library and pose them. To be safe, save your pz3 file. Resave under a different name as you make changes. When you're ready, render, and save that scene as a pz3 file.