That's a really great idea, that a Changling infiltrator set up the whole Valiant mission to, at least, get one of Starfleet's best combat ships and a bunch of promising cadets out of the way for a while, and at best get them all destroyed. Maybe Captain Ramirez was a changling and after he appeared to die actually just hung around looking like a piece of wreckage until the Defiant was out of sensor range and then turned into a form capable of interstellar travel. He told Watters that he was fully commissioned with the power to grant full commissions, and Watters believed him. That actually can save the episode from severe plot holes.