If he soloes a calamity then the calamities are weak as fuck, I mean he's been weakened quite a lot now while King and Queen have been chilling most of the time.
Only Jack put on some work but I doubt Sanji will fight him.
It's more likely he would go for Queen or maybe (but I doubt it) King. In any case, it would make the calamities look bad. Not that they look any good rn.