Scopper Gaban is a former Roger Pirate who appeared first in chapter 19 and his name got revealed in the One Piece Databook Blue Deep: Characters World. We have no confirmation from Oda that he will reappear, but it is possible that Oda layed clues over him for the future stories.
If we check out his name, we could easily tell that Scopper refers to “Copper” a part of “bronze”. As we know Silvers Reyleigh and Gol D. Roger’s names were references to “silver” and “gold”. For humanity precious metals. Based on this we can guess that Scopper could reappear and fulfill a similar role to Reyleigh, giving us more insight on the Roger Pirates and evolving the story in favour of the Straw Hats.
Copper and feudal Japan:
Here I want to give a possible theoretical connection between Scopper Gaban and Wano, before I go into plot details.
This is a Fuhonsen and one of the most important historical findings of japanese culture, especially if it comes to money, treasures and culture.
They are the oldest japanese coin and they are made out of bronze(copper).
Back in 687 they were cast then brought to imperial kingdom of Japan – “Heijo-Kyo” which turned out to become “nara” one of the periodically longer “existing” capitols of Japan. I can see Oda using this reference in Wano for multiple reasons:
1. Wano might have multiple references for multiple parts of plot and culture.
2. Wano is isolated, it is possible that they don’t have the Berry-system and rather their own currency and exchange-system.
3. This currency-system could be inspired by the Fuhonsen. And thus Wano is probably partially inspired by Heijo-Kyo/Nara.
Maybe this is delivering us the first reason why Scopper Gaban could be in Wano: Buisness and this could reflect probably Silvers Rayleigh on Sabaody Archipelago who also was there for business.
Rayleigh is coating ships in order to prepare them for a journey to Fishman Island/New World. I could imagine Scopper Gaban running a similair kind of buisness in Wano.
Wano/Sabaody parallel:
I believe some plotlines from Sabaody will be refurbished into Wano.
A great parallel for me is Rayleigh and Scopper. But is this everything? Is it enough to underlinde a possible Sabaody/Wano parallel?
As we know Law, Luffy and Kidd will all 3 participate in the events of Wano, as well as other Supernovas. So yeah there are more parallels to Sabaody. Also the aspect of “reuniting”.
So the expecting Scopper Gaban in Wano is not far off.
Oden Kouzuki:
We already know that the Roger Pirates had ties to Wano, Roger visited Wano, learned from their secrets and even Oden Kouzuki a Daimyo of Wano traveled alongside the Roger Pirates to Raftel.
Scopper Gaban and Oden Kozuki basically knew each other, also Rayleigh should know him.
After the disbanding of the Roger Pirates it could be possible that Scopper Gaban decided to reside in Wano, because it is safe, because he knew Oden and because he potentially could make the country stronger with building up a buisness and supporting the country.
I can’t speculate on what happened during or before Oden’s execution, but if Scopper was close to Oden, then I can imagine that Scopper also is hurt by Kaido’s actions.
I can imagine Scopper planning to take revenge on Oden and make Wano a better country without Kaido pulling the strings of terror on it.
Alliances:
Scopper Gaban could be a great help for the Straw Hats. But we don’t know anything about his personality. If he really wants to take revenge for a former Roger Pirate acquaintance, then he might have a plan. I wonder if Rayleigh also knows about it if he also might join in. I don’t want to deny this possibility, so we see both ex Roger Pirates taking revenge on Kaido for Oden.
Despise that I think the era of the Roger Pirates is over, they might show great feats, especially meaning Scopper, but he will fail against a tyrant like Kaido.
If the Straw Hats manage to take down Kaido and liberate Wano, then they might surpass the Roger Pirates at that point, or get at their same level. Just watching from a standpoint of parallels.
*Theory by Rej Discussions
