Picking one it would be Opoku.
Having said that I'd consider all of them. They were all very raw when they came here. I would imagine that all of them have probably at least doubled their total minutes in adult football. The experience will have improved them, and they all are young enough to improve further. Having said that,it's difficult to see any of them becoming regulars in the Prem. If they were available, you'd be signing players who wouldn't need bedding in to the team, the club or the area -much more attractive propositions than a year before, Obviously you're not going to sign all of them.
I guess it's possible that either Opoku or Watts might get game time with their parent club in the Championship, as might Fornah. We haven't seen a lot of Woods. but based on today he might be happier in a 4 than in a 3 at the back. Lewis is the one I'd have most concerns about - he's assertive in attack but defensively has most to learn.