I think the only thing left is for Ivankov to change Sanji's gender and he will be unstoppable.
There are already few hints for it in the story starting with Ivankov himself being a plot device capable of such.
The second hint is Sanji's destination during the 2 years time skip.
The next hint is Law swapping Sanji into Nami's body.
Followed up with Sanji gaining a bizarre power upon grabbing Nami's boobs and catching the dragon.
Lastly, the hint from Green Bull - if a pretty lady offered me food, maybe I would eat it.
The pretty lady is nobody else than our future Sanjina.
Sanji's evolution has just begun.