Oh my god dude, the ROBOT.
Its like you cant even think outside the box on why it exists here lmao. The pacifista arent necessary for anything. Any plot related excuse can get the crew away from the island without controlling any of the pacifista, and the Robot is one of them. Kuma is another.
Hell, if Kizaru is so conflicted, he could be a 3rd and betray Saturn.