Enjoy eating a Fan Cutter or Fan Lift if you guess wrong.
The ass as a Wake-Up, when timed right, ensures a good escape route, but it doesn't always have to be done as a Wake-Up. As long as you correctly judge the distance at which you will land from Sonya, she can't touch you. There ARE other characters with specials that can punish it, though...Sub-Zero's slide, Raiden's superman, etc.
As for the air fans, they don't exist solely to deal damage. They control space. You can walk and duck them, but a hybrid Kitana who knows how to abuse the range of her f2 1 and 2 1 will intimidate you from even trying to get in. There's also the problem that she'll build a good amount of meter by the time you reach her. One-bar hit-confirmable combos that lead to about 50% are not something I want to eat.