Also i could be wrong so correct me if so but...
Wasn't it said somewhere that oda wanted to make yami teach as strong as 3 admirals but changed his mind because it was too much too early?
Maybe he still plans on that being the case by giving him more devil fruits. Like if he gets a 3rd one it might be the case. Even tho thatd be beyond broken lol
At the same time it took both roger and garp to defeat xebec so it might not be totally impossible i guess
Maybe if oda legit decides to make him that stoopid strong again as strong as 3 admirals hell have him demonstrate it by actually defeating 3...
Again i could be wrong and i aint even really that hype on it but...it could be the case if he actually said that
If he didn't im just rambling random shit so im sorry lol