Sounds like his upside is a potential Jochen Hecht?
I'd say his upside is more of a hybrid of Jochen Hecht and Marco Sturm, if one wants to stick to German players for comparison.
If he pans out, he should be more of an offensive force than Hecht, and faster as well, although not quite as fast as Sturm was.
From what I have seen of him, he is gritty, works hard, he can rack up points when he has good chemistry with his linemates and he is a dangerous player on the penalty kill.
I really like his play with his backhand. I have seen him score quite a few goals with it, and he's also made some nice backhand passes when I watched him.
I heard from some that he will not make it as a top 6 forward in the NHL, and they could be right, but if he doesn't he could still have value as a 3rd line winger or center who excels on the pk and provides some secondary scoring.
I know nothing about Kessy so I won't try to say who won or lost the trade, but I think that Phoenix got themselves a pretty good prospect. Now it will be interesting to see how they develop him.