Have you read “Originals” by Adam Grant yet? If not, I strongly recommend it — it has lots of really insightful advice on how to be innovative. One of his pieces of advice is that assigning dissenting roles is not very effective, since it serves more as a fig leaf (“yeah, we considered the opposite case too, let’s move on”) than a genuine discussion starter:

Stop assigning devil’s advocates and start unearthing them. Dissenting opinions are useful even when they’re wrong, but they’re only effective if they’re authentic and consistent. Instead of assigning people to play the devil’s advocate, find people who genuinely hold minority opinions, and invite them to present their views. To identify these people, try appointing an information manager — make someone responsible for seeking out team members individually before meetings to find out what they know.

This is only the summary version, there is more detail in the book.

Now, this might not really be relevant for the teardowns, but in thinking about how to manage creative dissent, I think it is tremendously useful advice.