In an alternate universe, their relationship could develop in a very different way. For example, if the wizarding world had no concept of pure - blood supremacy, Draco would not have the same prejudices he had in the original story. He might meet Tonks in a more positive setting, like at a magical research facility where they are both working on a project to improve inter - magical creature relations. Their relationship could start as a friendly professional one, and over time, they could develop deeper feelings as they discover each other's strengths and vulnerabilities.
In an alternate universe where magic works differently, say spells are more emotion - based. Draco, who is often reserved about his emotions in the original story, has to learn to be more open in this new magical world. Tonks, who is very in touch with her emotions, could help him. They might meet when Draco is struggling with a new emotion - based spellcasting technique. Tonks offers to tutor him. At first, Draco is reluctant but soon realizes that Tonks has a lot to offer. Their relationship develops as Draco becomes more confident in his new skills, and he starts to see Tonks in a new light, leading to a relationship that is based on mutual growth and respect.