The ability to load in a second (3rd, 4th, etc) character previously created in Poser, that can be manipulated like the present one.

 

At this point, it would appear that the only way to get 2 or more characters (like people, not simple objects) in a scene is to start them both in the same scene, or import the other as an object which cannot be repositioned. The other option is combining images outside of Poser. When working with the same characters in multiple scenes, I could load another M4 and type in all his morph values in a fairly reasonable time, but would need to start the hair pretty much from scratch, which is the most time-consuming part of the process. And once hair is made a Prop, (I think) it can no longer be manipulated for a different pose.

If Poser has another alternative, I'd love to know it!

(Currently working in PP2012.)