I've been studying the yin/yang principle. The idea of taking someone's balance doesn't seem to fit this. Every time that I think about it, I come to the conclusion that if my attitude is to take the other person's balance, then I am essentially trying to make the black side bigger than the white, or visa versa. Yin/yang also seems to be a principle of making one out of two. When I think about the concept of me trying to be balanced, and off-balancing the other, it's more like one side is clobbering the other side no matter how smoothly some can make it look.
I say this because I started to think that maybe I can look at this from a different refernce point. Maybe both sides should be trying to balance themselves with the point of contact, or some center point somehow. That way, even the uke can in balance even if they are upside down in mid air. From this perspective, I'm not sure that anyone can really take your balance from you. It's more likely that you can loose your frame of reference from which you balance yourself- the other person's movement can make it easy for that to happen.
Just a thought.