Surely the reason for having the FE is to monitor the systems on the FE panel and take appropriate actions if things start to go pear-shaped?
I can quite believe it would be possible to operate a 3-crew aircraft with 2 pilots in normal circumstances, but in an emergency situation?!? Would you really want one of the pilot's to unstrap and play at being the FE while the other pilot flew? Surely that would remove a lot of the safety that comes from having the non-handling pilot watching, assisting and cross-checking the handling pilot's actions and decisions.
I would definitely not want to be on an aircraft in that situation...
