#2 Ronda Rousey vs Shayna Baszler
These two members of the Four Horsewomen have been through a lot together, and that goes for their time in pro wrestling in addition to what they were able to accomplish in mixed martial arts.
Both Ronda Rousey and Shayna Baszler could quite easily rule their respective kingdoms for as long as they choose to do so, but the real moneymaker would be to have them square off against one another in an MMA fight. While Ronda may be the clear favorite when you compare their records against one another, we've just got a feeling that she'll be more than a bit anxious to step back into the cage after what happened against Holly Holm and Amanda Nunes.
Baszler, on the other hand, would have nothing to lose. There's an argument to be made that these two would never agree to square off in such a setting, but if WWE wants to ensure that the fans are given a fight that's worth their time, these two will almost certainly be able to provide that service.