"I think that one, and perhaps the major reason for the framing device is that it allows the show to be done with a small cast of eight and, in a full production, with a unit set. The thinking may be that it would make future productions more feasible."
I think you're right that this is the justification for the framing device, but I still don't think it was necessary. As I said in my comments about the show on our "This Week on Broadway" podcast, I liked some of the rewrites but I greatly disliked others, including that "I Want to Kill Her" number in Act II, or whatever the title was. Such a huge mistake -- I'm amazed that the original number was rewritten in that way.