I agree, I can even make an argument that no star could co-exist alongside Harden under D'Antoni's offense. Unless of course, you are willing to stand up in the corner/wing and jack up 3s while Harden has been dribbling for 20 seconds already.
Now on the trade, if Sam Presti and the Thunder are indeed ready to move on and rebuild their team, they would want from Houston multiple 1st round draft picks and a third team to pick/absorb CP3's huge $124m contract (lol good luck with that).
As a realistic destination for Westbrook, I can see that being Miami.