#3 Stephanie McMahon
Like her father, Stephanie McMahon has also been a guest referee previously. In fact, it was a match featuring her husband, Triple H (although they were not on the same page back then), and Kurt Angle way back at the No Way Out PPV in 2002.
Stephanie could insert herself in the match to sway the odds in her husband's favour by becoming a referee for the match.
She already has huge heat from the WWE Universe due to her ejecting Becky Lynch from her match at WrestleMania against Ronda Rousey, while also having troubles with Rousey. She is currently a heel in the WWE, and she could maybe use her heelish ways to help her husband win the match as a referee, which would make things very interesting in the match.
This is a match that will mostly go in the favour of Batista, and with the odds against his favour (if there is a special guest referee) the crowd will be cheering for him to triumph.