At the moment he is a walk-in spot for wing. Mitchell has some work to do to become a contender again, when he regains his form its going to be a tough decision but at this point in time JOC (James O'Connor) is definitly a walk-in (especially with his recent wallaby performances - he has outplayed his opposite number every game, maybe with the expection of the ABs).
Yes he has enough pace - like mentioned above refer to him leaving Shane Williams in his dust, also refer to his try saving tackle verse Ireland where he came from the other side of the park to chase down the Irish winger.
With the modern roaming winger role, he is far from wasted on the wing. In fact combined with his JOCs selfishness (he constantely wants the ball in his hands) it suits his style perfectly. Where other wingers dont get involved enough, JOC (James O'Connor) will always be looking to get involved due to his selfish attitude.
Maybe one day we will see him at 12, but until then he's perfect on the wing. (However I do like the combo of a 10. Barnes 12. JOC (James O'Connor) for this RC)