Seems to me that (though it probably won't happen) it would be a pretty good move for both teams. Nash could give NJ the outside shot (the shot that was absent throughout the finals, and that was preyed on by the Spurs) that they desperately need. Nash also fits the Nets' running game, since Dallas's type of game is fairly similar.
The same can be said for Kidd, who would go from one running team to another, so the transition wouldn't be problematic. Kidd could give the Mavs some half-court stability too. But one of the main things Kidd could bring to the Mavs is his rebounding capabilities. One of Kidd's main shortcomings is his outside shot (or lack thereof), but the Mavs already have a plethora of outside shooters to knock down those treys. Nash would be more at home in NJ anyway, being from Canada and all anyway

. Though unlikely, it does seem like a pretty equitable trade to me...