I think a first officer "designation" is a great idea. It would certainly help missions make more sense. It's kind of odd that I've left an Ensign and a Commander on my starship, yet the Ensign is the one who's always in communication with me about trouble brewing in space. The Commander I leave behind NEVER says anything, even though he outranks the Ensign and should logically be in command of the ship.

As for the mechanical aspects of a first officer, well... I'm uncertain of that.