Sanji would be much weaker if he had trained his CoA hardening or CoA barrier to be durable, rather than his genes that he activates with his emotions.
Sanji would be much weaker if instead of advancing his flames (Ifrit jambe), he did advCoA or CoC training. Sanji is not the type of character...
I think it's your willpower/determination that strengthens the exoskeleton, not the haki
In fact, it would be interesting if the power of love (exoskeleton and ifrit jambe) was Sanji's unique way of expressing haki. It would be much more original.
Would the exoskeleton be the most demonstrative way to express your emotions, your love?
It seems that when Sanji's heart heats up to a maximum level, his eyebrow changes direction and then he begins to express more of the power of his genes
Since Sanji vs Seraphin Jinbe, which Sanji called his defense "power of love" it is obvious that he is enhancing his genes (scientific power) through his Sora power of his emotions with his burning heart.
That burning heart, power of love, the power to protect people with his empathy makes him...