Despite his deficiencies, Leddy has a role and his speed is a necessary element for this team, but if they could put Leddy in a package for an upgrade defensively, I would be fine with that. Get a top-2 defenseman, add Toews into the starting mix and let Hickey/Pelech alternate.
The Isles would have to find a top-heavy team looking to add some overall lineup balance, receiving a Leddy+ package, or a team looking to shake up their core. Muzzin would be a good target, just not sure what, alongside Leddy, it would take? Muzzin is a UFA after 2019-20, so that is a consideration for both teams as well.