Yeah i agree.
It is the most hyped ability in the manga , probably how the 20 Kingdoms were able to take down the Ancient Kingdom.
Also Mihawk definitely has CoC & Double Layered Eyes.
When do you think he would fight Zoro?
I also agree with your opinion on how Shanks & Mihawk mirrors Brook & Zombie Ryuma with Brook later saying he never used his full power on me.
But with so many different factions in the Final Arc (Blackbeard Pirates, Im & Gorosei, Holy Knights, Seraphim, Admirals) where would Mihawk & Cross Guild fit in, in your opinion?
I don't think Ancient Kingdom is Destroyed, it's just Hidden similar to Shandia
20 Kings instead Inherited CoC from the one responsible for destroying "Land of Gods"
And i also don't believe Lunarians Kingdom is called Land of Gods, Oda mentioned together simply cuz Lunarians Inherited this Kingdom's Will
(Lunarians are inspired by Seraphim who are inspired from Angels who serve God)
Double-Layered Eyes are like Dragon Ball Fusion
For example, if Cavendish & Hakuba settled their differences they would Unlock those Eyes (Similar to Chapter Titled Half & Half)
But there will be Two Fusions, either One where Canvendish in Control or One where Hakuba in Control
Literally similar to difference between Gogeta & Vegito
So technically, you could say Mihawk we've always been seeing is like Vegito & He is on Shanks Level
Zoro will instead face the other side (Gogeta), exactly like Zombie Ryuma who hid his True Power Level
As for Final Saga being Overcrowded, i believe it's Split in Two, we are now witnessing Mary Geoise Arc & the Villains are Imu + Davy Jones.
And then We will have the True Final Arc in Elbaf against Sea God & Sea Devil.
So some Factions will still survive this World War & appear in Elbaf Saga (Where entire Existence is at stake)
Cross Guild is gonna be one of those surviving Factions, i believe they will succeed & they gonna replace WG
Buggy's Plan to claim the spoils of war will come True
Other Factions will also survive, only WG are going down this Arc.
(Possibly Titanic Captains are also going down + Akainu will lose his Fleet Admiral Position. But BB/Akainu will still be Villains in Elbaf Part)