While conditioning is a concern, I don't think it's a big one. It's the sort of thing that should be able to be rectified, and if it isn't, then there's a much deeper issue - a lack of work ethic.
I remember scouts were really concerned about Brenden Morrow's conditioning at the same age, and while Morrow is a guy who is natually a little pudgy, he worked very hard at getting his weight down.
Bourret has a lot to like: good speed, good skill, lots of aggression. He has a history of putting up points. Once he learns the value of spending time in the gym, he'll be fine. I think he can be a gritty second line scorer at best, a grinding energy player at worst. I can't really speak on his performance in the A this year - haven't seen him play or read anything on his performance - but 32 points in 45 games for a kid who turned 20 when the season started is a good start to a pro career.