The worst part about the makeover is that Merida's hair was a huge technical achievement for Pixar (watch a clip carefully to see why), and Disney airbrushed it out.
Their movies are great as a computer person and moviegoer, since each usually contains at least one "wow, that must be really hard with computers" moment. Like the fur simulation in Monsters, Inc. or the crowd physics(ish) simulation in WALL-E, or Merida's hair as you mention. Not to mention the incredible render quality progression from Toy Story to Toy Story 3.
Who cares if it was a huge technical achievement? Why should that make a difference to Disney or kids who love Brave?
I can see it now: "Girl With The Pearl Earring: Bratz Doll Edition".
I watched the movie awhile ago, but I remember that you could really see how much effort and character they put into her hair. That and the bow are the most distinctive parts of her character design.
It's a cartoon rendering--a different canvas if you will. It wouldn't make sense to have 3d hair with inertia strapped to a painting. (Though there was some success in Treasure Planet).