Arlong stated himself he needs to kill Zoro right there and then (what should you take from this scene ?) that Zoro isn't a threat ??
Doriki argument is piss poor not addressing that when there are so many holes in it 2200 vs 4000.
(i.e. one is a brawler the other is a swordsman who is ranked without his sword)
They are relative to each other
I'm supported by databooks and character statements in the manga you're supported by head canon. (GodTier is a tier only EOS characters reach btw) sure most likely Luffy will be there but he won't be alone.
Zoro is secondary. true but that doesn't take away the fact he will be WSS which in itself is GodTier.
- Zoro is the first to unlock CoA (not Luffy)
- Zoro's introduction arc is him taking down the main antagonist (meaning when needed Zoro can step up and take the MC role when needed Zoro himself chooses not to)
- Zoro's Asura is advCoC (first to utilize CoC not Luffy)
- Zoro fighting Kaido and scarring him is only done by one other person (Oden) not Luffy
Luffy being the MC argument is asinine, Zoro has done things before Luffy and vice versa this has been happening since CH#2 why ignore something so blatant
Zoro being a threat isn't the same as Zoro being capable of taking Arlong down; that's what Luffy can do, the interdependence speech is quite straightforward. The moment Zoro can kick Arlong's ass too, the moment the whole meaning of the scene falls apart.
Doriki is what it is, a direct hierarchy that was meant to portray who is stronger and who is weaker. That's his narrative intent, what Oda is trying to tell by creating such system, unless you believe what he intended to do was to completely confuss the reader so the message he received was the contrary to what he actually wanted.
Zoro "wasn't the first to unlock CoA"; I can assure you "armament haki" wasn't even a thing back in Arabasta. Zoro taking Morgan down wasn't about strength but support (what it meant to have a crewmate watching your back). I will give you the "advCoC" (if it's even advanced instead of just an insight on how to use that power) but it's far from clear, and I'd love to see Luffy scarring Kaido (or anybody, for the matter) with punches.
This isn't just about Luffy being the main character but what being
One Piece's main character means. Luffy's dream requires topping the rest of supreme kings, according to Chinjao's words; Luffy is the kid-looking guy who was born Children's Day and has a childish dream the Pirate King shared with him; he's more than likely the next Joy Boy, a prophesied comer, and wears a Straw Hat like that guarded by Im among all. And I can guarantee you that whatever Luffy is destined to do, he isn't going to do it with kind words but by force, by winning, by being stronger, because this is a shonen and that's how he solves things.
Again, Zoro can't even dream of being relative to Luffy. Noone in the crew can. This is his story and sooner or later he will top any conqueror out there for sure while Zoro keeps getting the Hatchan, the Mr. 1, the Kaku, the Pica, the King or whatever subordinate significantly weaker and less important than Luffy's adversary.
Whatever "GodTier" the WSS is (and you speak of headcanons; your own terms are made up), it won't be comparable to what Luffy is becoming when this manga is over and we don't post in here ever again.