Saturn vs the ancient robot is probably the most obvious match up of all time at this point
I'm convinced that Saturn is the person Bonney wants to kill. Saturn is the Warrior God of Science and Defense, and has authority over the Pacifista/Kuma. We know Vegapunk is familiar with the Gorosei. Since Saturn is focused on Science and Defense, it makes sense he was involved of the development of the Pacista.
Saturn is the man who turned Kuma into a cyborg.
BUT. What if the ancient robot was the same? Franky's bad ending is becoming an robot then robot ship. What if Saturn is from the Void Century... and he turned the ancient robot into a cyborg, just like Franky. The ancient robot was climbing Mary Geoise to murder Saturn, just like Kuma, for turning him into a robot slave.
When Luffy fought Lucci, and the Drums of Liberation played, the robot didn't activate.
What changed from Luffy's first fight to the second? SATURN'S ARRIVAL. IT WAS ONLY WHEN SATURN ARRIVED, THAT THE DRUMS OF LIBERATION ACTIVATED THE ANCIENT ROBOT.
Kuma and Ancient Robot vs Saturn, let's get it.