I wish they hadn't made Merida an official Disney princess for this very reason. She's not the type of princess that fits for the intended purposes of Disney Princess marketing. I also hate that they semi-include Mulan in this line for the same reason. In regards to these two characters, Disney has completely miss the point as to why they should not be included in the line.
I know that they are both strong characters that could help even out the balance in comparison to other characters but the marketing of the line has lacked bringing the characters' personalities into the mix. It's mostly about the looks and dresses. If it was about the personality, Merida and Mulan would fit.