I really wish they upgraded the iPad mini last year to match the specs of the air. I went with an Air but still find it a bit clunky. I'd gladly trade some battery life for the awesome form factor of a 6.1 mm thin mini with touch ID.
I traded in my iPad 3 for an iPad Air 2 and really couldn't be happier with it.
I'd love to see an iPad mini as thin as the Air 2, even if that meant a dramatic reduction in battery life. It would be the perfect device for reading (though probably not for text entry).