I don't know why everyone wants a Sanji powerup when Brook and Chopper have drifted next to or below Nami in terms of fighting ability. Like, Chopper somehow found a way to nerf his strongest transformation (but hey, at least he found out how to control his now-irrelevant transformation, right?) and all Brook did was figure out how to actually use his fruit in a quasi-useful manner. >Can we, as a subreddit, finally just acknowledge two things in regards to Sanji?
1) Sanji was injured when he fought Vergo.
First of all, after Nami wakes up from the explosion from Caesar while she was in his body she says, "I really damaged Sanji-kun's body."
Then Oda decides to bring the event up again and once more point out the injured condition of Sanji's body because of the explosion. Sanji: "Huh?... All this damage to my body can't have been from that one blow..." Usopp: "Ah, Nami got really messed up by Caesar when she was in your body."
These sorts of things don't get brought up for no reason. That little punch from Nami left him really hurting because his body was already badly damaged and Oda went through the trouble of pointing that out for us twice.
2) Vergo is probably Doflamingo's strongest executive.
Putting aside the fact that he's a stronger CoA Haki user than Smoker(and probably better than Luffy too), is a Rokushiki master, has a mix of long and short range attacks, and is possibly a life return user as well(remember how he got noticeably bulkier when he got serious with Law?), he is also the original heart seat who Doffy sent to infiltrate the marines(a very important mission) and was Doffy's very first crew member.
The combination of this knowledge should change your perception of Sanji's fight against Vergo.
Sanji was definitely injured pretty badly before fighting Vergo, Doffy's right hand man and one of the strongest CoA users we've met(who may also use Tekkai). Yet he was able to fight him for a short time and even kicked him through the wall not once but twice before his leg started to give and the fight started to favor Vergo.
The only fights Sanji has gotten so far in the New World were Vergo and Doflamingo himself(and against Doflamingo he had no idea what Doffy's powers were and Doflamingo even complimented his strength). They are (most likely) the two strongest guys in Doffy's crew and he was at a disadvantage against both. And put up a damn good fight against Vergo all things considered. Yet people say Sanji is weak and needs a power up. I think it's silly and people are really being fooled into underestimating Sanji. He's extremely strong just like Zoro and Luffy are. Even if he is still behind them it's not by much. The Straw-Hat support staff blows ass, man. /rant