Here's my tuppence. Ok first of all
Someone would have to hit me or effectively distract me to actually take my balance
Well yeah. That's why we have atemi. Whether you regularly apply them in class or not, atemi should be a fundamental part of how you think about all your techniques. Second of all,
I honestly think when an average person senses imbalance, they will react in a way to try and regain balance and if they have any sense of self-preservation they will resist you from the beginning.
Well they won't resist you in the beginning. Because if we remember in the beginning
they were busy attacking you. Which is kind of the point. They aren't focused on their balance, they are focused on punching your teeth out. They lose their balance because of how you react to that. Either because the solid object they were expecting to hit is no longer there and they over reach, or because you've cut them to an unbalance point, or because you've thrown an atemi or (most likely) all of the above. But surely then they should recover their balance? Not only does aikido allow for this, it downright depends upon it. Take the classic example of irimi nage. It is uke's attempt to recover that leads them into the throw. Pretty much all our techniqes are designed to exploit the natrual self preservation instincts of the majority of people. The most trouble I have with uke's is when we are going too slow and they are overthinking how they should
be reacting rather than just moving.
Of course developing to a level where your timing and blending is good enough to move seemlessly with uke is tricky. But as they say, if it was easy, everybody would be doing it.