#4. Asuka
Asuka has lost a lot of momentum ever since her undefeated streak came to its demise. She was the first ever Women's Royal Rumble winner and now has been reduced to almost a comedy act after being made to look like an absolute fool against Carmella. She can regain her rightful credibility by becoming the first women to defeat Rousey one on one.
A good way to book this would be to let her turn heel and start winning for a while. She can then be drafted to Raw next year. By Summerslam, while Ronda would have defeated all possible opponents for the title, a renewed vicious and unforgiving Asuka would challenge her for the title. They would then go on to have a fantastic match together with Asuka beating Ronda Rousey.
The question is how? Well, I suggest as Asuka is a submission specialist, this can happen in one of two ways. First, a steel cage match, where Asuka can escape to win and second by locking Ronda in the Asuka lock and referee calling for the bell without Rousey tapping on Stephanie McMahon's orders just like the Montreal screw job. This can lead to a deadly alliance between Asuka and Stephanie and they can then feud with Ronda.