I really don't see the point of trading for Smith. Flames have enough depth on defence right now. Honestly, I would rather they just sign Nakladal for extra depth if that is what they need.
Smith is intriguing because he can play a decent physical game, but he hasn't quite developed into what people thought he would. Jokipakka I think is probably a better and more consistent defencemen than Smith, so I would look at Smith in the middle-pairing as a downgrade, though very fine for 'depth' and with the possibility of improving considering age and past expectations.
Wotherspoon, Kulak and possibly even (if you believe the Flames) Kylington will all be getting some time up on the Flames this year. I would rather just go with what they have, unless they can find a clear young upgrade somewhere.