I think Duncan would be great, in that he plays the Nate Way, plays the KP way, and wouldn't have to be the #1 option playing 42 minutes a night like he does now. He's steady, experienced, and a winner. His game is predicated on being an "old man game" anyway, so I think he'll be able to age gracefully by playing tough D and hitting open hook shots and bank shots when other teams double Greg.
Kidd would be a one-year rental, but I think what he brings is what we need. A winner, a PG that can direct this team, and just enough of a defender still to stay on the court. But I don't think he wants to come here. And it's not like he'd play 40 mpg.
Unless PHX keeps playing the money game, I wouldn't give what they'd want for Nash. But if a 12M trade exception call Raef LaFrentz looks good to them, then Raef+Bayless+Frye/Diogu/(Maybe Outlaw) for Nash and Grant Hill would be fine for me.