I don't think it is a typical situation, there was an expansion draft, and given the freshness of the organization, they probably felt like it was better to have a captain than not. Most teams do not go several years without a captain. Gio had no ties to the organization or the city, he was simply just chosen in the draft. This + his contract situation makes him likely to be moved IMO. Seattle is no Vegas and they need to find a way to avoid turning into a Phoenix situation. If they can get reasonable assets in a trade, I would move anything not bolted down.
Regarding the Leafs, He would be a modest upgrade on the backend and definitely help with the culture that they should be trying to set. Not sure what the leafs could move for him though, he wouldn't come cheap, probably something like 1st, Sandin, and some salary.