I'd probably trade Hagelin for Ladd. It's easier to find a Hagelin than a Ladd. They might very well have a better version of Hagelin with Duclair.
Ladd would be a piece I'd definitely have interest in. I don't know if WPG would be so willing to trade their captain and if so for so little (would you want just Hagelin for Callahan?). But if he could be had for the right price that's certainly a winger with size, scoring ability, and a bit of toughness that this team needs.