...I don't understand the point of this.
Both Iverson and Gordon are unrestricted free agents.
It would allow Chicago to give AI more than the MLE (or save Chicago from having to use its MLE on Iverson), and it would permit Detroit to give Gordon more than an 8% annual raise (they could give him 10.5% raises if he's signed by Chicago). Also, if Detroit wanted to, it could give Gordon a sixth year if Chicago traded him to them.
What I don't get is, didn't Detroit have to renounce AI in order to have all that cap room?
Another potential benefit to the Pistons to a sign and trade is that they could in theory sign an additional free agent and then do the sign and trade for Gordon. I mean say they want Marion or Kidd. They could sign that guy and Villanueva and then sign and trade to get Gordon and thus get that extra free agent.