I made a theory 5 years ago about a possible transformation of Sanji alluding to Lucifer:
https://worstgen.alwaysdata.net/for...-in-a-supposed-transformation-not-in-rs.5744/
This was long before Sanji destroyed the raid suit
I also started from the premise that Demon King > Diable. So, I thought the Lucifer transformation would come right after the diable jambe, but Oda introduced a high-ranking demon in the middle (ifrit)
Going further now, a Luciferian transformation, whose name would be ''Devil King'', with Sanji shooting CoC flames, and increasing all his abilities and manipulated genetic statistics.
Now with all this power of love stuff that Oda is introducing to the character of Sanji;
In some modern readings and philosophical interpretations (such as the thoughts of certain authors such as Friedrich Nietzsche or even the Lucifer series, based on DC Comics comics), Lucifer is portrayed as a figure who represents liberation, autonomy and even reconciliation with one's own human desires. In such approaches, Lucifer's "love" is no longer just selfish or manipulative love, but a deeper form of love, aimed at self-acceptance and the recognition of human complexity.
Lucifer, in this view, could be seen as someone who, in his desire to experience freedom and true love, defies convention and authority to give others the chance to live their own lives without fear of being punished for their mistakes or desires.
Come to think of it, this deserves a much better elaborated theory about Sanji's future power up, as soon as I have time I'll update my theory