Speaking from my own viewpoint, I consider the whole plan to be very poor from the get go. It's reliant on things that Sylvanas has no real control over, such as how the Proudmoores react to seeing their own dead and the method of trafficking Derek is also very unclear. Even then, the impact is only there with a profound stroke of luck, say Derek offing Jaina while she's unaware or being able to use her fleet-control pendant because he's also a Proudmoore. It was a crapshoot and even if it were successful it wouldn't have been worth the huge amount of friction created by making a spectacle out of the guy's torture.
From a story perspective though, I don't think he's conditioned because much of the evidence for it is circumstantial. Things like the placement of hte boat that could just be Blizzard's use of assets, as well as how emotional the scene with Jaina is meant to be and how he's put away from any Proudmoores. His real purpose of the narrative if you ask me is as an introduction to Calia and her role in the Horde. I don't think he has a part to play in the Alliance, simply because despite Jaina's extreme tolerance for him, she makes a point of how he can't come back. Similarly, there's no reason to assume that Sylvanas is aware of Calia. Certainly if she is she's an Arthas-like figure to Sylvanas, threatening her on a basic level that I doubt she'd be able to act with as much restraint towards.