Since the Kings just let McLemore go last summer, I don't think he really is in their plans.
By my math, the Kings could trade McLemore, Labissierre, and Hayes non-guaranteed contract for Melo, a first round pick, and a future 2nd.
The Kings buy out Melo, get a couple of draft assets, and clean up the roster a bit.
The Thunder shed something like 20 million in luxury tax payments, get a rotation two-guard to fill in while Roberson is out, and get a 12th man in Labissierre.
Plus, this takes away the last team with significant space that can offer Smart a contract.