I wouldn't be surprised at all by a Flashpoint event, yeah, but even if they don't, honestly, so what? How many different ways are there in comics to snap a hero back to their default setting? Practically the entire mechanism of comic book storytelling is set up to facilitate this. You don't need a universal reset button to do it, and no, it doesn't matter how significant their sins are (an entirely separate debate, since they are saving two entire universes with every Earth they destroy). It's very rare that an explanation is so bad that it retroactively ruins the story that preceded it, and nigh-unheard of that such actions lead a character to an irredeemable place. Jean Grey destroyed a planet...so? Plenty of great stories came out of that and the character recovered just fine, even if the rubber band snapped a little too hard on that one as they set her back in place. She bounced back. Gwen Stacy and Norman Osborn having sex was a grotesque act of character assassination, but it didn't make the bridge death any less poignant, nor did it seriously interfere with Norman's capacity to be a convincing egomaniacal villain. Finally, isn't the ultimate point of no return for a literary character death? How often do we overcome that little hurdle?
Writers should always feel free to go as far as they need to with these characters in telling the best story they can possibly tell, the story they really want to tell, even if they only have a very loose, flimsy idea of how they are going to snap that rubber band back. Maybe they fail to reset the character properly, and are forced to mothball them for a period of years (i.e., Hal Jordan)...does that mean it wasn't worth the story? As long as the story was good, and worth telling, I would say the answer is certainly no.
Thus, while I also suspect this is part of a grander plan to realign the Marvel universe (likely to more closely resemble the MCU), I don't really care if Hickman's solution to this "de-heroification" is lame. The story he's telling now is incredibly epic, satisfying and unlike anything I've read before from the big two. That should be enough for anyone. Hand-wringing about the future of Tony Stark and Reed Richards isn't something I am about to start doing. Hand-wringing over the future of Namor? No no no. Come on now. He's more compelling with a streak of villainy anyway...let's see him go straight antagonist for a few years. Why not?
Edit: ha, I had the exact same read on the Cannonball/Sunspot situation
This is exactly it IMO. I like the double-think that's involved. THIS is OUR reality, we know it to be real and for 7 billion people to be on the planet. This alternate earth... what do we owe it? is it better for 14 billion people to die instead of just 7? What if it's an earth filled with douchebag supernazis? Our priority should be our people, we should be prepared to kill to save our reality.
Yes! Exactly. These are the sorts of questions I find so compelling in these books, and I will kill all of the sacred cows to see them explored. All of them.