I think it would be nice to have other choices too. I'm fat in real life and I'm comfortable with that fact. For the brief period that I played Second Life, I made my avatar fat too because I see no reason to feel ashamed of the way I look. I would love to have the opportunity to make my New Leaf character fat too.
Disabled characters are rarely represented in games. It would be nice for AC players to have the choice to show their avatar using a wheelchair for example.
I suggest that if you feel this is wrong, as I do, that you write to Nintendo and express your views. Perhaps someone can work out how to get a petition going?