I think we have to look at the rest of the movies for context as to why I think casting Stone as Gwen was a mistake. Sure, casting Stone as MJ wouldn't have saved those movies from the terrible parents subplot. But it would have kept up interest as they moved into ASM 3.
See, for all the "world building" they were trying to do to turn ASM into a mega franchise to compete with the MCU, they didn't build up Peter's world. In fact, they reduced Peter's world going into ASM 2 with Flash Thompson's disappearance. And cutting out the scenes with Shailene Woodley as MJ. And keeping the Bugle entirely off screen. And the mess that was the Harry Osborn story. (He was supposed to be Peter's BFF? Didn't even get mentioned at all in the first movie.)
See, I agree it's a "good problem" to have the audience care about the characters and what happens to them. It's a "bad problem" when that's the ONLY thing they care about when they plan on killing off the character. And in these movies, Gwen ended up being a BAD PROBLEM. (Capitalized for emphasis.)
As has been said, the romance angle wasn't a major selling point of those franchises. Romance has been a major selling point of the Spider-Man films since the first Raimi film.
MJ's dad being a complete jerk is pretty much a constant through the Marvel multiverse. What he actually does as a job? That one's up in the air.An ASM with Stone as MJ probably gets you Stone as the Ultimate MJ, which would still be a very similar character. The main difference would be in Captain Stacy, although I'm sure they could figure out a way to figure out an authority figure who doesn't trust Spider-Man.
(But I always love it when Jonah rallies the public against Spider-Man.)