I hate Kidd, like really hate him, but he is 100 times the player Marbury is now. Like, at least Marbury did the Starbury shoe thing for Steve and Barry's (totally not enough padding in the heel btw, in any of the models), but his game is so far over the hill. He might turn it around slightly with D'Antoni in town, but it would take a lot more than Marbury for Kidd straight up.
And as for Dallas needing a shooting pg- they already have the ultimate one in Jason Terry. They are a solid team, as is.