I am for a defensive coach, but I actually don't think Martz would be the worst idea in the world. At least he is a true wizard on one side of the ball, and look at his record with quarterbacks. He's done a great job with them, and if you see Romo's development as a critical component of the job, we could do a lot worse than Martz.
I do hate how he doesn't care at all about game management or resting his defense, but who knows, maybe he learned something after getting fired from the Rams. It wouldn't be the first time a coach learned from his mistakes and was better the second time around.