I was not a lot happy about it at the first time, but with more time passing I'm starting to appreciate it. It gives Sanji new life as a character and we can even expect new things in the future.
I still don't like 100% the thing that he is "in fact" a modified human like his brothers, but still this point is obscure. If the modifications are all about Exoskeleton, we could say that Sanji is not always like his brothers and not always "modified". I know it's hard to understand it, how his Exoskeleton "grows" everytime his eyebrows change? His brothers have the exoskeleton from birth and they have it all the time, but Sanji's one seems like "growed" after using the raid suit a few times, but for some reason it disappeared.
It's weird, from wikipedia "An exoskeleton (from Greek έξω éxō "outer" and σκελετός skeletós "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human ." So how Sanji exoskeleton grows? Is this shell like bones appears on top of his normal bones? Oda will never explain that, I'm pretty sure.