Powers & Abilities According to Oda, Shanks CoC = Rayleigh CoC

[Romsteack]

You are talking about first mates, whether "fodder randoms" or not. Aladine was never compared to Jinbe in the way Jinbe was compared to Tiger, yet he was Jinbe's first mate. Mohji's captain is Buggy, one of the most relevant pirates in this story, and we know he has been put as way more comparable to Cabaji considering their draw in their fight for captaincy. Regarding Boo, he's obviously way weaker than Sai considering both characters importance plus their performance against the Funk brothers. Sarquiss clearly didn't stand out compared to Bellamy, and Jango was Usopp's versus while Luffy took care of Kuro himself.

First mates are never portrayed, let alone confirmed, to be close ni power to the captains; and I have huge doubts about the likes of Rayleigh or Zoro (who isn't the first mate but the combatant, anyways) being close to Roger (whose only explicit comparison was with Whitebeard) and Luffy.

As I said, you made things up and went for some biased cherry-picking.

Well if u want i'll only talk about Beckmann, Rayleigh, Zoro and Jinbe

First of all Beckmann is the First Mate of Shanks. “Even the warriors of the ‘New World’ shall tremble upon the man who rival ‘RedHair’...!!” Beckmann is comparable to Shanks confirmed.

Jinbe was the first mate of Fisher Tiger and stated as strong as Fisher in the Manga.

Zoro is the first mate of Luffy ( yeah sorry he was stated as the vice-captain in one of the databook red or yellow ) and is said to be as strong as his captain. ( You could say this is just Pre-TS but anyways. )

Rayleigh is the first mate of Roger and is said to be a legend like Whitebeard by Garp himself ( Garp fought with Roger in death matches many times so they're basically equals ). You could say this doesn't confirm anything but i don't agree you're not a legend like Whitebeard or Roger if you can't compete with them.

So i don't know why you said first mates were never portrayed close to their captains in strenght because in fact they are. You could also add Kidd and Killer who are always together and like Luffy and Zoro are supernovas

Seems like your headcannon went out of his way and not my... biased cherry-picking ???