Huberdeau, yeah. I think if I had to re-do it I'd put him on the team over Hall.
Barzal over Couturier I think doesn't make much sense. Over the last three years Couturier has scored 211 points and won a Selke(and finished top 10 in voting the other two years). Barzal has 207 points with significantly fewer goals, obviously not as good a defender and significantly worse in face-offs.
Honestly, Barzal's not really on my radar. There are some guys nobody has talked about(Schenn, Couture, Monahan) who I'd probably put above him.
Yeah. Each will have varying opinions on which players should occupy and round out the roster. I'm particularly bullish on Barzal as a whole, so I'd have him higher up on my list than others like you would. But, at that point, it's splitting semantics when you have that many options including those other guys you mentioned.
As long as it's not like a Zamuner-esque addition such as Tyler Bertuzzi or something to muck things up, you really can't go wrong with all the players at the country's disposal.