Bruh akainu was obsessed with dragon in MF. Dragon was also a marine at one point.
Why shanks vs garling is not possible?
I think koby's main fight will be against BBPs and not WG.
Venus most likely second/third strongest gorosei
Yeah, ok, let's drop the Dragon vs Akainu talk (or any Akainu vs talk that is not Akainu vs Luffy) because I wholly disagree with it and no one can really change my mind about it.
Now, maybe Shanks vs Garling is possible if Shanks is still alive by then, but that would leave Shamrock to Koby. After all, Koby isn't sitting out the fight against WG, dude, even if Koby does fight the BBPs.
Look, even if you are right and Zoro vs a Gorosei is an actual possibility, you still need to accept the fact that Zoro isn't going to vs someone stronger than Law's opponent/Kidd's opponent. Wano proves this already and if you're not buying this, then you are arguing against the manga's own content.
So, if Nusjuro is 2nd strongest Gorosei like you said, that means:
Dragon or Sabo or Shanks vs Gorosei 1
Zoro vs Nusjuro
Law vs Gorosei 3
Kidd vs Gorosei 4
Dragon or Sabo or Shanks vs Gorosei 5
That match-up isn't happening because no way Lolda would highlight Zoro over Luffy's peers like Sabo/Dragon/Shanks who have far bigger hype than Zoro has ever received.
Now, if Nusjuro is 3rd strongest Gorosei, the line-up looks like this:
Dragon or Sabo or Shanks vs Gorosei 1
Dragon or Sabo or Shanks vs Gorosei 2
Zoro vs Nusjuro
Law vs Gorosei 4
Kidd vs Gorosei 5
Again, impossible because Law and Kidd's opponents will always be stronger than Zoro's.
Your Zoro vs Nusjuro hope is only possible if Nusjuro is the weakest Gorosei, which ensures that Zoro isn't gonna outperform Luffy's peers (Pointing out to Wano, I hope, being a devoted Yonko fan, you don't genuinely think beating King was more impressive than beating Big Mom), with this line-up:
Dragon or Sabo or Shanks vs Gorosei 1
Dragon or Sabo or Shanks vs Gorosei 2
Law vs Gorosei 3
Kidd vs Gorosei 4
Zoro vs Nusjuro
And we know Zoro is never gonna have the weakest of a group as his main fight.
Just to clarify, though, I don't think Zoro vs Nusjuro in the Final War is absolutely impossible. I think there is genuinely a 2-3% chance of it happening (slightly smaller than Zoro vs an Admiral at 5-6% chance). But that fight will necessitate Lolda to overturn a pattern he has steadfastly been holding for close to 30 years.