Models aren't meant to represent 'everyday women' (whatever that means). They are meant to be prettier than you. That's their job. The tricky thing is that, because of the nature of fashion, what constitutes being beautiful or pretty is constantly changing. An example: here is Diana Mitford who was widely considered to be one of England's greatest beauties in the 1920s and 30s:
I don't think many of my contemporaries would consider her looks to be ideal.
Similarly, I remember a bit of dialogue in the 1958 film Gigi, in which the title character (played by Leslie Caron) complains about her legs being too long. Here is current supermodel Hana Soukopova:
These days I don't think there's such a thing as 'too long' when it comes to legs.
The reason I'm in favour of designers using larger models is that I think we're due for a change in the popular fashion silhouette; the super-skinny look has been in for about twenty years, it's time for something new. Perhaps in the future (though I can't imagine it will be too soon), a shorter figure will become fashionable. If this does happen, it will necessarily mean that tall models will be out. Fashion can be mean like that.
So how about this: forget 'fashion should embrace fatties'. Never mind having 'real women' in magazines. Don't bother yourself with 'put shorties on the catwalk'. Not everyone is beautiful. This is OK. Let's embrace being ugly.