Even when you think of our only other comics red head - Black Widow - they did integrate her more glamourous side into the character we got in the movie.
"Only other comics redhead?" What about Jean Grey or Mystique? Or Banshee or Daredevil? Or Jimmy Olsen? Not to mention the huge number of redheads who haven't been in movies yet -- Medusa, Rachel and Hope Summers, Carnage, Barbara Gordon, Lana Lang, Poison Ivy, Wally West, Batwoman, Miss Martian, Guy Gardner, Mera, Red Sonja, Caitlin Fairchild, etc.
Redheads are disproportionately common in comics, partly because of the limited color palettes of old comics, and partly because red hair is visually striking. Heck, even Lex Luthor was a redhead when he had hair.
Don't get me wrong, I have no problem with a non super-model MJ it's just... hey she was a model and actress in the comics for almost 30-40 years - nearly as long as she's been around. The ore "brainy" MJ is still fairly 'new' - even if it's a concept that's almost 10-13 years old at this point.
Okay, there's a certain logic flaw here. What I'm hearing is "This MJ must not be an actress or a model because she looks like Shailene Woodley." But... Shailene Woodley is an actress -- otherwise we wouldn't be talking about whether she's the right person to play a character in a movie. In fact, she's a rather successful actress who's been getting a whole bunch of awards and nominations for a few years now. And she has, in fact, been modeling since she was four years old.