From what I read, that's not really how it goes down (I'm talking about the picture of Flash Thompson from the Ultimate Spider-Man cartoon) and he's not all that interesting. You'd be better off with the Punisher.
Feige himself stated he wanted there to be stories from Spidey's teen years, so yeah, he's guilty of that atrocious line of thinking.
Maximum Carnage was fun as fuck to read, I loved it, but yeah, as a story arc it would be ridiculous to have as a movie. Maybe an animated one where you didn't have continuity restraints.
I want them to get Venom's origin RIGHT for once, damn it. That's why they should not have gone straight into Infinity War and done a Secret War first. Get each of them to set foot on an alien world, test them for survival when the only stakes are their own lives, use the opportunity to introduce some new characters while they're at it, some aliens and such, to build up to Infinity War where the alien villain isn't so much more like a leap up the mountain rather than a hike up the slope.
Much as I like Ultimate Spider-Man (the cartoon and the comic), none of his story arcs are worth putting to the big screen, at least none of the ones that didn't involve cameos by one or more of the other big heroes. Grown-up Spidey having marital difficulties, an elderly relative to worry about, and having to be a lower-middle-class guy struggling between working and being a superhero, now THAT is something the other Avengers never have to balance in their day-to-day lives. Is that really any worse than him having to worry about being late for school, sleeping in class or forgetting to do his homework? Kids are going to see fucking Spider-Man whether or not he's their age and I can prove it: A woman brought her goddamn six-year-old to Captain America the Winter Soldier for Christ's sake (and the little bastard wouldn't shut the fuck up the entire time.) Captain America's a grownup with literally nothing in common with the average person today of any age, but had no problem in attracting a wide audience. Spider-Man would be no different, in fact, he'd probably be a sight better. If you're going to make him be in high school you officially have to start calling him Spider-Boy. How much box office would a name like THAT attract?