My technique is "soft" in that I'm not using much of my strength trying to muscle around uke or Nage. There are others in our group who are not soft at all, despite the fact that our instructors teaching style leans towards the softer styles. In practicing soft style I have not found them to be weak, but quite the opposite. I've been thrown more then ten feet by someone who barely touched me. I also have fewer problems working with those stronger and taller then me, focusing less on trying to push my weight and force against theirs.
In regards to Aikido and Ballet, I practiced ballet for many moons. A lot of my movements in Aikido tend to fall back on the postures and the like which was taught to me by my heinous teacher. Sensei often tells me to "stop dancing around" as I pivot into techniques and generally move. One thing I've noticed in people, ballet experience or no , is the standard toe lift. Unless you are very very balanced, walking up on the flats of your toes does not bode well.
Just a few thoughts,