If this scenario were to happen, then Lee would very likely win this matchup. The only thing Sanji has over Lee is much stronger kicks, probably on the level of Tsunade, though Lee is highly proficient in the use of kicking himself, so he should have little problem trying to adapt to his fighting style. Lees biggest advantage over Sanji is his speed. He can move so fast that it is very hard to even follow him with the naked eye. While Sanji is considered to be pretty fast himself, his speed feats pale in comparison to Lee when he took off the weights. Sanji can only do that because he is able to repel the air/water hard enough to actually cause a shockwave to propel himself forward, not because he does it fast enough.
The main reason why Lee would win is because of gates. With the power of the gates, Lee could match Sanji's leg power and proceed to blitz the hell out of him. He is literally untouchable in this mode and only tekkai users, gear 2nd Luffy, and Kizaru could match his speed. he will die for sure once a good front lotus lands. if he does survive, (99% chance he wont, cause breaking the neck is an instant kill) then the reverse lotus will finish him.
