You get that Sanji has to rewrite or turn off his DNA to deactivate the exoskeleton. Thats what the Germa scientists said after all.
And nah Haki can’t block Kizarus beams
Sanji's science upgrade is actually super cool because of this:
Just like Devil Fruits, he has to alter his Lineage Factor/DNA in real time to use his powers. BUT, because it's not a Fruit, Sanji doesn't have to worry about sinking, and can still swim.
Sanji's Exoskeleton functions just like a DF in terms of altering the DNA to activate it.
I give all credit to Sora and none to Judge, Judge can eat bricks covered in Big Mom's... okay, I'm not going to finish the sentence, but you can imagine how it might have ended.
Sora is the best, underrated One Piece Mom