I personally prefer this: http://schpog-art.tumblr.com/post/41893331484/askhumanappledash-aj-since-so-many-of-ya-were
and this: http://askhumanpinkiedash.tumblr.com/tagged/character-concept
but those are a little too detailed for flash, so maybe this PSG style one: http://soundmonkeymediamadness.files.wordpress.com/2013/02/bcgn7t7cuaaxoj_-large.jpg
I do think that it would have been better if they risked it with the skin colors. In my personal headcanon, the skin order would be Pinkie(super pale to the point that it looks pinkish because of the blood), Rarity(pale, but with some color), Applejack(tanned caucasian), Fluttershy(light olive skin), Rainbow Dash(dark tan), and Twilight(black).
They should also give more variety when it comes to their bodies. In my headcanon, Pinkie Pie would be chubby, AJ muscular and a little chubby on top, Rarity and Fluttershy are slender with curves, RD is lean and toned, and Twilight's a thin pear, but like the skin tones I'd be curious to see what they'd do with the bodies instead. They're probably similar because it's easier to swap out clothes, but if the clothes are cloth like barbie clothes, then there can easily make minor differences without it being too bad. Plus, it'd be interesting if each doll had their own set of clothes that could be identified by the size and style, and dolls of similar size could share clothes but it won't always fit, like an AJ outfit would be super huge on RD.
Even so, I understand why they did what they did and it still looks nice, so I'm not complaining. This is just what I would have done if I was in their shoes!