Sora got the drug from Vegapunk, right?
Maybe, but I like to think that maybe Sora had some scientific knowledge of her own since I can't imagine Judge marrying someone out of love (unless he was a pervert like Sanji when he was young) and the comic character Sora Warrior of the Sea (who Morgans maybe based on Sora?) had what looked like a laser gun, but knowing Oda he might simply do an SBS or one shot panel showing Vegapunk giving the pill to Sora in a flashback. I mean its possible Sora may have met both Judge and Vegapunk through MADS I guess.
Tbh my thought is that Sora has a lunarian ancestor.
Judge purposefully chose her as his wife because he wanted to see if he could create children with that power.
The exoskeletons are an attempt to awaken the dormant lunarian abilities which is why only the vinsmokes have the exoskeleton and not any of the clones judge makes.
Because of the medicine, sanjis latent lunarian ability was never activated until sanjis emotions triggered that ancestral power in the form of DJ.
This definitely seems like the most likely scenario. I can imagine Judge only married her just for her genes (and other sciency or supernatural secrets we might not know about) just so he could use her to increase his army's power like the heartless jackass that he is.
The exoskeleton stuff makes sense, but if a Lunarian's fire indicates the exoskeleton is active, then why don't Sanji's brothers have some kind of fire too and how come Sanji can use his while not on fire? My personal guess is that maybe since their genes are dormant or imperfect then their exoskeletons are still inferior to a purer Lunarian's. So they can manifest a weaker version of the exoskeleton, but until they learn how to light the fire on their backs (flaming halos/auras?) they can't become as invulnerable as a Lunarian?
I hope that's the case since that would mean Sanji's endgame form will get some kind of Lunarian fire aura and maybe even flaming wings (haki/spiritual/physical?) to show that his full exoskeleton is completely active which would be pretty cool and a flaming angel form would compliment Luffy's deity form, Zoro's asura form and Brook's soul king form.