A few main reasons:
1. Elbaf is set up as one of the most impactful arcs of the series so it needs an equally large villain which leaves BB, Shanks, or Akainu
2. Akainu imo fits the best as Elbaf is connected to Norse mythology which the end of days in Norse mythology ends with a magma giant destroying the world
3. The World Government has been connected to Elbaf during Elbafs first introduction in Big Moms flashback as we were shown that the World Government uses mother Carmel in Elbaf to buy children for Cipher Pol.
4. So WG both have narrative reason and access to Elbaf.
5. And the only villains we have that are worth anything in the WG is the admirals and the gorosei and the holy knights. And of those three gorosei makes the most sense as it’s too early for Zoro and Sanji to fight admirals and the holy knights seem like they’d be better for the revs since they’re already being connected to them. Plus with the loss of Kizaru, and Fuji and Ryo occupied, there’s no one else.
All in all I feel like Elbaf is going to become the next tournament of extermination because they have Oharas knowledge, lucci told them it’s the straw hats next location, and if the straw hats take Vegapunk and Bonney there then it’s likely where the revs will come as well for the fights of:
Luffy vs Sakazuki
Dragon vs Garling
Sabo vs Warcury
Zoro vs Nasujuro
Sanji vs Mars
Ally vs Ju Peter
Revs and Straw hats vs Holy Knights
1. Elbaf is set up as one of the most impactful arcs of the series so it needs an equally large villain which leaves BB, Shanks, or Akainu
2. Akainu imo fits the best as Elbaf is connected to Norse mythology which the end of days in Norse mythology ends with a magma giant destroying the world
3. The World Government has been connected to Elbaf during Elbafs first introduction in Big Moms flashback as we were shown that the World Government uses mother Carmel in Elbaf to buy children for Cipher Pol.
4. So WG both have narrative reason and access to Elbaf.
5. And the only villains we have that are worth anything in the WG is the admirals and the gorosei and the holy knights. And of those three gorosei makes the most sense as it’s too early for Zoro and Sanji to fight admirals and the holy knights seem like they’d be better for the revs since they’re already being connected to them. Plus with the loss of Kizaru, and Fuji and Ryo occupied, there’s no one else.
All in all I feel like Elbaf is going to become the next tournament of extermination because they have Oharas knowledge, lucci told them it’s the straw hats next location, and if the straw hats take Vegapunk and Bonney there then it’s likely where the revs will come as well for the fights of:
Luffy vs Sakazuki
Dragon vs Garling
Sabo vs Warcury
Zoro vs Nasujuro
Sanji vs Mars
Ally vs Ju Peter
Revs and Straw hats vs Holy Knights