Sanji doesn't really have regeneration. Or, he DOES, but its not what people think? Germa regeneration is like....you get shot, then heal up perfectly by the following day, like Reiju after what happened with Pudding. Its not near instant regeneration from any injury like what Marco has, its just enhanced natural healing speed. Its just that people tend to mix that up with the weird exoskeleton shenanigans, where for SOME reason they can get their skulls caved in and can just.....buff that shit out like dents on a car (now, their internal organs should probably be turned to mush by that, but.....One Piece logic? 😅). Lmao. Which isn't regeneration, its more like they're just not taking damage normally in the first place.