#1st, Comparison
Marineford was the place of the war that should be protected. So Shichibukai & Admiral cant have a match on another place.
Had Navy get Rayleigh, it would Akagami Pirates duo with WB come to Navy.
That wasnt wise.
#2nd, the confidence over the grandson
- Sengoku talked about Wano with Akainu even a little. Garp might knew as well. 'There must be several samurai' feeling.
- SH had 2 arc that looks good. 1) Won over Doffy 2) Won over 2 SC & escape from WCI
- on Wano there are 8 supernova, & 6 of them on different side to Kaido
Thus, any force that consist of buster call with an Admiral is enough