I mean We have an Army of Kuma as WG's Smile Army, We have Clones of Warlords as WG's Tobbi Roppo,
We have Shanks Twin, We have Stussy Clone, We have Gorosei who i won't be surprised if They were using other People's Bodies ... etc
I can definitely see Holy Knights made of some Characters We know who were given Power & Brainwashed,
And everybody knows that i'm far far from being a Kid Fan, but i'm starting to believe that Lucci/Kaku of Holy Knights are gonna be Kid/Killer,
Meaning it's possible that Kid/Killer on Imu Steroids or Potential Unlocked or some DF Powers ... etc are gonna be Luffy & Zoro's Next Main Opponents
So it's really possible that Gunko might be that Girl from SBS,
Currently, until We see new stuff or new reveals, i support the idea that Kid/Killer are Future Holy Knights & when They are Injected with that WG's Endgame Buff, They are gonna turn out to be their Greatest Success, just like Lucci/Kaku in CP-9
Hody/Hyouzou were New Arlong/Hatchan,
Doffy/Pica were New Crocodile/Mr. 1,
Kaidou/King were New Enel/Ohm,
Kid/Killer are New Lucci/Kaku,
Moria + Oars/Zombie Ryuma are New Final Villain (Whoever it is) + Blackbeard/Mihawk
This is My Current List,
So yeah, i think your Theory is very Possible,