I see half of them also as Mario characters and half as Sonic. Twilight/Blaze: New girls,purple,a bit unsocial,can use magic,calm,culturated. Pinkie Pie/Amy Rose: Funny,pink,a bit childish but cute. Applejack/Cream: Has a big family,orange,always to help her friends.
Fluttershy/Peach: Caring,loving,pink and yellow,graceful. Rainbow Dash/Daisy: Tomboyish,tough but friendly,colorful and rowdy. Rarity/Rosalina: Motherly,the eldest (i think Rarity is the eldest of all ponies and Rosie is the eldest between all those Mario/Sonic girls),elegant,fashionable,a bit dramatic.
Not exactly sure, I guess as fans it would be funny to see just how much Pinkie Pie will annoy him, some even suggested that Amy should be with her and Rouge should be with Rarity; which is actually far better than what I picked, but I could still find a way to make it work.