You see that quite a lot nowadays where full backs are either used or like to think of themselves as wingers or "wing backs".
Personally if a player is part of the back four and therefore a defender I want his main ability to be good at defending rather than seeing him whizzing up and down the pitch.
Good examples would be both Peltier and McNaughton - defending was their task and they were good at it. Whenever they went over the halfway line you'd be screaming for them to give the ball to someone else who would know what to do with it but as no nonsense pure defenders they were both excellent at what they do.
Defend first - the fancy stuff can come later or from somebody further up the pitch.