Here's an idea...let's take a pilot COMPLETELY out of the loop...oh yea..he falls asleep for 15 minutes..what if the other one does too? Then we're at the same problem.

What if there's an emergency, and the newly awoken pilot now has to re-orient himself to an ever changing situation?

I'm sure the PF will be glad to give the PNF a full brief while he's trying to bring the airplane out of a dive because of rapid decompression.