Vader wasn't fully cremated. The helmet surviving is indicative of this.
Besides if you're wearing a helmet, and areas of it start to melt it's very likely that those places are the the ones that will be the most scarred/burnt as that's where the heat was the most intense, as well as having the plastic/metal burn through your skin as well. I thought that was obvious?
My issue with Snoke being a new character is that he's very old and very powerful. What the fuck has this guy been doing for the last hundred years, since he's said to have been alive before Anakin's birth. Who trained him?
How did he become so powerful? How did he become leader of the remnants of the Empire?
Like what the fuck? Super powerful badass comes out of NOWHERE to rule the Galaxy? What kind of bullshit is that. That's like Rey's parents turning out to be Michael Jackson and Lisa Marie Presley's daughter.
If he isn't someone we've seen before, whether it be Sifo-Dyas (who built the army needed to save the Republic, but was kicked off the council, disgraced, and left for dead), Plagueis, Vader, another former Sith, or maybe a former Jedi, even Ezra Bridger, then it's going to be dumb as fuck and disappointing to a lot of fans because we've seen that mastering the force requires training.
...wait, how can we even assume he's powerful? Fuck this guy could be an imposter, or have the Force Sensitivity of Jar Jar. I mean there's no metric if he's new. Plagueis (in any form) would make him the most powerful villain in Star Wars continuity, which is badass, and would lead to some very dramatic storytelling. That's why so many people are attached to that theory, because it's fucking great if he has survived this entire time, unknown to the Jedi/Sith.
Palpatine and Vader were awesome villains, and now we get Kylo Ren (a whiny little bitch) and Supreme Leader John Doe? Woopty fucking doo. Is that what you guys really want? Really?If that's the case, Luke should be able to fuck this guy up unless there's some stupid backstory of him being an ultra-Dark Sider who stole Doc's time machine and traveled into the future or something really stupid. If he's Plagueis, then even Luke is outmatched. I mean the guy is only the most powerful force user in canon. More powerful than Luke, Anakin, and Yoda.
He's the ultimate villain in a saga known for its villains. There's no way he's a new character and they create enough backstory in the remaining two movies for it to be remotely satisfying. If he is John Doe, then how did he become so powerful? Let's turn Star Wars into... "yeah, everybody who is force attuned can automatically shoot lightning bolts out of their ass, like Rey learning how to do shit without guidance." Now we have Snoke who is automatically assumed to be the most powerful Dark Side user in the Galaxy, awesome!
I don't give a fuck, as long as he's not a new character. I do not want the final villain in a 9 movie series to be a random fucking guy. I want him to have been around since the very beginning and there to have been some reference to him in at least one of the movies before VII. Sifo-Dyas would be just as awesome as Plagueis.