Luffy and Nami would feel extremely weird imo, they really have that sibling energy between them, more than between any other male and female in the crew. Even Luffy x Robin would feel less weird imo.
But yeah, the kiss between Sanji and Pudding pretty much sealed the deal. Plus the fact she's the only girl who fell for him and she's a chocolatier, which screams "they're gonna open their own restaurant and live happily ever after".
Their children are gonna look weird, though. Three-eyed girl/boy with swirly eyebrows, an exoskeleton, super strrength and possibly emotion-based powers.