I think it's a great idea.
I have used some of hassan's techniques on the dubs when they call on me, and once you become aware of the dual personality thing, it is easy to tell which "mode" the jw is in when they are talking to you.
The best you can hope for is a flash of the authentic personality coming through every now and then. They are usually very quick to swith back to the dub personality. But I consider every one a victory.
I had a sister calling on me for a while. One day she brought a bored, distracted, polite young brother with her (maybe 20). You could tell he wasn't really paying attention to our conversation. But at one point, I asked the question, "If the majority of mankind is displeasing to god, why did he create us that way?".
The sister said "he gave us freewill, and the majority choose to sin".
I said, "so why did he create us with the kind of freewill that makes the majority of us want to disobey?"
She had a couple of more twists on the "freewill makes it our fault crapola", and I just kept saying "so why did he create us that way".
At one point you could almost literally see a lightbulb go on over the bros head, he suddenly sat up staraight and looked at me and said, "wow, you've really thought about this haven't you!". For a moment you could actually see intelligence in his eyes, then after a moment the glazed look came over him again.
I consider that a victory, I doubt he will soon forget that "aha" moment.
It was an accumulation of those moments that got me out.
