I understand why you say that with what we have so far Paperchampion and your analysis of the current events is not wrong at all, in fact I agree why you say that.
Now, I'm more looking at the bigger picture of the situation and my arguments mix both of current events and predictions of the future events.
To me, Saturn has yet to show what makes him eternally young / immortal and what makes him a Gorosei. The current chapters have already showed to us his insane regeneration abilities and it won't stop there.
Remember that Saturn told Bonney that if it hurt him, he would have dodged and he hasn't dodged anything yet and has only been regenerating, that gets to show you how insane he is if he yet has to care about the punches people land on him.
I think Saturn may even be unbeatable and the only counter to him may be the warrior of liberation that fights as he wishes and manipulates the fight.
Bonney will punch Saturn, Robot may also get involved who knows, but it'll only hype up Saturn and tells us that the only solution is Luffy/Nika.
We will learn about Nika's devil fruit with this confrontation.
We may even understand why Kizaru is a cog in the machine and doesn't want to betray Saturn, maybe Kizaru knows what Saturn is capable of and he doesn't want to betray him yet.
The only answer to Saturn is Nika, that's what Kuma's flashback has hyped us for, that's what an immortal elder who knows Nika is going to face.
You don't bring an elder who knows about the void century so he falls in the hands of somebody else that is not Nika.
Luffy will crush Saturn like an "insect" with his foot and destroy even Egghead in the process in an attack named "Bajrang Stamp" or "Bajrang Axe", similar to the attack that Kuma saw Luffy train. In Hindu mythology, Lord Saturn is associated with Blue Sapphire, which is Oda's reference for that. What is even more striking is that in that same mythology, Bajrang Bali (Hanuman) steps onto Saturn and puts him under his mighty feet to control him. Bajrang Bali and Saturn, the connection runs deeper than him being crushed like an insect, which would be the most satisfying outcome of the arc.
Given that Saturn is most likely going to be defeated by Luffy, I only see Zoro defeating Kizaru.
If Saturn has yet to show us his real abilities and the ancient robot has yet to move, it means the arc still has a lot of chapters left, meaning that Zoro can defeat Lucci (or not) and then come back for Kizaru.
Luffy defeated Lucci then Kizaru then will defeat Saturn.
Zoro defeated Kaku, then Lucci then may finish Kizaru off.
Sanji imprisoned Kaku, faced Kizaru and then may finish Lucci off.
This will even mirror Sabaody with Zoro having his revenge on Kizaru and having his Rayleigh moment.
Zoro uses "3 sword style" and "9 sword style" technique and Kizaru has shown us that he can create light clones that all own a sword so Zoro is the best match up.
Zoro fighting Kizaru goes beyond that. Zoro has to channel his energy to cut light and that makes him more likely to get black blade in the future. Zoro can't just go and land an attack like "Divine Departure" because the cut is not clean and it will not cut light, it will only cut Kizaru. So, he has to learn how to channel that blade energy to make a clean cut on light.
If you don't believe me yet then let's take a look at Zoro's potential opponents until the end of the story.
- Zoro cut a rock in Dressrosa (Pica)
- Zoro cut fire in Wano (King's flame)
- Zoro may cut light in Egghead (Kizaru)
- Zoro will cut "nothing" / invisible human (Shiryu)
- Zoro will then fight Mihawk
- Zoro will cut diamond (V. Nusjuro) - either before or after Mihawk (but I have it after)
Rock -> Fire -> Light -> Nothing -> Mihawk (best swordsman) -> V. Nusjuro (diamond + best swordsman ever)
Kizaru fits perfectly as Zoro's opponent, he is his next element to cut, like he says it clearly: "there is nothing I can't cut"
