DJ has nothing to do with his modifications until now, its all about "emotions", it may be correlated with his enhancements, but it doesn't look like he should be able to use fire according to his Germa epiteth "Stealth Black".
This is exactly what has been confusing me too. I hope him using fire is connected to CoC or at least CoA somehow, preferably CoC though. Maybe it's more so to do with Lunarians somehow though, something to do with Sora as we know so little about her too?
She seemed to be human but what if she's not? Just a similar human-like race, the Lunarians maybe? I looked it up and her race isn't mentioned, I'm guessing she's just presumed to be human for obvious reasons ofc? She has no Vivre Card yet either as far as I can see, so maybe this will end up being deliberate and important too as it will give her true nature/heritage away maybe?
(Too wild lol?)
It's very confusing anyway....I just wish Oda would explain what Diable Jambe actually is, did Sanji just invent it himself inspired by Wanze as Luffy seemed to get inspired by Blueno/CP9 for Gear 2nd I think? Or is there a lot more to it than that? How can he use it without spinning now and even generate flames all over himself? Why don't they burn him too? How do his emotions come into play here, how do they cause and effect them?