I think when the dragons were born, he and Daenerys could have become closer. Viserys would have regained hope and no longer needed to press Dany to do whatever needs to be done to get power. Remember, he didn't do it because he liked to be mean to her, but she was too young to understand the need for those actions. He was pretty much the father role in a way.
So they would firstly go to Qarth and do pretty much the same, I think Astapor will change the story. Viserys and Daenerys would really work together here, both speaking Valyrian, and he would be delighted about Unsullied. If Daenerys would have been able to convince him to go to Yunkai and Meereen, even better. Viserys could be the one explaining Daenerys the need for slaves there, he wasn't all that against slavery. I guess that the slaves would not have been freed with Viserys there.
But Viserys would never have it allowed to chain the dragons.
Viserys didn't know he would have to marry Arianne. But if some envoy from Dorne would have arrived, likely Arianne, as Quentyn was not promised in such a scenario, Viserys and Dany would go. And then the war begins. Pretty much this.