The truth is he's never been one. His strengths were always his safe hands. He went years between dropping a ball, when most fullbacks drop a kick every other week. He was a safe last line of defense and had that knack of being there in the right place at the right time. A few years ago his lack of pace wasn't an issue as we had the likes of Lyon, Albert, Gidley etc out wide to cause a threat.
If you compare Wellens' performances recently to Brett Hodgson's or Clint Greenshields'(Out of contract this year by the way) you will be able to see how lacking Wello is. He's always arriving as the opposition player is touching the ball down, he no longer has that knack of being in the right place and he is starting to make basic mistakes at an alarming rate. His chiming into the attack is another area where those two mentioned destroy him. He labours onto the ball and although the angle is good he has absolutely no pace so ends up putting the centres under all sorts of pressure with a nothing pass.
If I were Royce I'd have Makinson at fullback. I don't care if he drops a few bombs at the start, he can practice those. He'd add so much to the attack, chiming in at pace.