It's funny that some fans say that sora wanted her children to be humans, yet at the same time think she belong to some ancient race of gods.
Sanji is a 100% modified human, why would oda make his body react to the raid suit otherwise.
Sora protested against her children being made emotionless and obedient, so she took the medicine.
At the flashback judge gave his children one command "discipline", it was the thing that sanji lacked, when his brothers were studying he was playing with a turtle, he never paied attention to classes, he got scared during training, he was cooking for a rat despite his fathers orders against it. Sora's medicine made sanji defiant and emotional. Sanji only disciplined about the things he likes, in baratie it was heavily established that sanji was causing troubles for zeff due to his defiant nature, he even picked up smoking against zeff's wishes...
In the flashback there was scientists who suggested they should give sanji more time for his abilities to develop because his bloodline element was successfully modified but it didn't manifest, it was judge who gave up on him.
I read some prediction about "sanji fusing with some fiery bird/suit, not obeying orders".
That goes completely white what i said, sanji's power comes from his emotional and defiant nature, unlike his siblings who's powers come from obedience and being emotionless.