No coincidence Jack is at the heart of so many "what will be" debates (who will he replace, where will he play, who's best model for development, etc.). His skill set makes this like a 360 degrees thing: while with most you can point at specific strengths (and weaknesses) and point at a likely direction, with him this is almost unlimited.
I was personally a bit surprised by the way he was used upon return from his loan, but you couldn't argue with the impact and his level. You can't argue with his natural skills on the ball, passing - anything, really. True, we've yet to see him scoring and doing some killer stuff in the final third - but would anyone dare exclude he can develop there too?
At this point I can see why people take to the Arteta direction. But to me this could go in many other directions.
