Keero lovers-to-enemies-to-lovers roadblock 1: the more I think about it, the more I'm convinced that if either of these characters went through a profound enough character arc that it turned them rebel, they just wouldn't like each other anymore.
Like, they both see each other as manifestations of an ideal that they associate with the Empire. From Syril's POV, we get this clearly signposted in his S1 confession to Dedra. We don't get enough Dedra POV on this or in general, but when she's happy for Syril in the Partagaz threesome scene, we can infer that his dream is her dream too. She too gets off on being a willing weapon of the Empire and she loves Syril by giving him that experience, even though she agrees with Partagaz that he's not well-suited, it's a dangerous mission, and they have to be apart for years. So if these two ever stop projecting their weird mommy issues onto the Empire, what remains as the basis of their relationship? Is there a there there?