Southee has been leading our attack for a while. But his talent isn't the same as McCullum's. And he has been frankly irresponsible many times with the bat. He could be a decent bowling all rounder with a bit of application to his batting. He's got a good eye, just needs defensive technique.
It is interesting.
Baz was an incisive player. I don't know that Southee is that. He's a hard working player, but he can't bowl at 150+ and he can't bowl that many unplayable deliveries. That's what Baz was. When he batted at his finest he was simply unplayable for any opposition. And he batted at his finest reasonably often in the last few years.
Who does Hesson want to captain? He's the other unmentioned (and kudos for him for managing to step out of the limelight) quantity here. He and Baz were definitely a team and a double act.