Oklahoma City Thunder
At first, I included the Oklahoma City Thunder because it would be super cool to see Russell Westbrook head back home. He became a star in OKC. He is still beloved by the fans. The Thunder are the only team out of the five that could do this trade exceptionally easily. They should reunite with Westbrook and together, deliver a Championship to this awesome fanbase.
The Thunder don't necessarily need another backup point guard. Westbrook needs the Thunder to win a Championship more than they need him. But it's hard not to get excited for nostalgic sake, or from a talent perspective. Westbrook fits in on this team nicely. Isaiah Joe, Alex Caruso, Aaron Wiggins, and Jalen Williams are all good three-point shooters who can provide him with his iconic drive-and-kick play style.
The Thunder not only have the perimeter shooting players required for good scheme fit, but they also have the perimeter defenders as well. Hartenstein, Chet Holmgren, and other Jaylin Williams provide solid interior depth, while Caruso, Wiggins Cason Wallace, and Lu Dort provide very good-to-elite perimeter defense. This would be an awesome scenario and one I'd love to see happen. The Thunder are close to being Championship-caliber and Westbrook could be the missing piece.
Winning a ring together after years apart with the Thunder would be an unreal storyline. However, wherever he ends up, Westbrook deserves a Championship ring. Any one of these five teams would be lucky to have him and he'd be lucky to find his way on any of these five rosters. Mutually beneficial.