Shanks is Related to World Government
Same for Law & Cross Guild
Same for Blackbeard & Revos
Same for Bonney & Vivi & Wapo
Same for Neo Mads & Vegapunk
... etc
All Players of this Arc have a Story to tell or at least a Sub-Plot related to World Government or a Faction of it.
Kid have 0 Connection to this ongoing Plot, that's why Oda forced him Out
But He will return in Final Arc (Oda simply showed us why Rayleigh's Suggestion Pre-TS was Important)
I even questioned his Involvement this Saga like Months Ago
This leaves us with Kid, not sure if he will appear this Arc, cuz maybe while everyone is fighting, Kid will take the opportunity to roam freely and build a Pirate Army (Similar to Shiki), so that he returns a bigger Threat in Elbaf.
Oda also Reversed Kid & Luffy's Order of Events
Luffy's Journey got Ruined ---> Decided to Train on Haki & Prepare ---> Participated in a War where He Awakened his DF
Kid Participated in a War where He Awakened his DF ---> His Journey got Ruined ---> He will decide to Train on Haki & Prepare
We were even given a Hint on who's gonna Train them, it's Man marked with Flames
Most Fans think it's Saul but i'm fully Convinced it's Rocks D. Xebec who is now working for Elbaf's Royalty
(Basically think of Xebec as Kuro & Elbaf's Royalty as Kaya Family)
This is also why Kid was taken down near Elbaf + His Ship got Destroyed meaning He ain't going anywhere
And Oda clearly showed us that Dorry/Brogy who are from The Village don't care about them
But a Man living with Royal Family will care for them
Oda also tricked Fans into thinking Xebec wanted Empty Throne when in Reality He wanted Elbaf Throne
But this is a Story for another Time