Hmmm... so you are taking a very business-oriented mindset to it, trying to use challenges as a way to discover what makes people more productive &/or seeking opportunities to get work done.
Allow me to play devil's advocate..
I could perhaps see it a different way, where we use the challenges more for the fun of it. Learning about people's interests, what makes them unique... less of the hardcore "achievement" side, and more of the "fun stuff that makes life worthwhile" side.
Examples of this might be:
(1) Who are your favorite band? Tell the story of how you discovered them.
(2) What's the strangest fun thing that ever happened to you?
(3) What is your weirdest hobby and why?
I'm interested in digging deep in the strangeness of the human condition - those odds and ends that make us all who we are. Just another idea about it. :-)
RE: Sndbox Challenges – My suggested roadmap