Speculations Greenbull's fire resistance sets him up as a Sanji opponent. Sanji will raise his flame's heat to eventually win.

Sanji can already break GB's defence (the wood defence, not his Haki) via his flames.
Momo was confirmed to be a weaker Kaido (dragon form, that attack specifically).
On the other hand, this ofc doesn't mean anything (something like Sanji has a chance now).

So no, your theory makes no sense.

P.S: not saying GB won't be Sanji's Admiral rival, there are arguments for it. But this is not one of them.
 
Bro he put bounties on the marines and got assistance from Mihawk and Crocodile. Of course they'd call him an emperor. He might not be that strong him self, but he has strong allies, territory, money and fame. All of the things needed to be a Yonko
Government still thinks he’s top tier
He has a band of infamous criminals, allied with Wb, former apprentice on Rogers ship, even saw him scalding Shanks in Marineford.
 
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