Re: Defending against Aikido
All kaeshiwaza depends on regaining your balance. In fact, I'd stick my neck out enough to say that what distinguishes aikido techniques is the strong emphasis on kuzushi (not to say that judo/jitsu doesn't have it).
If you're off balance, and the aikido is good, its already over, regardless of the technique. You just can't do iriminage if you're spinning on one foot. In this situation, all you can try to do is regain your balance. Unfortunately for you, most aikido training assumes an uke who is trying to do just that, so you have your work cut out for you - good aikido doesn't allow uke to get back to their center. This means that good aikido doesn't have kaeshi openings.
I don't really have much to say to people who said that you can't be attacked with aikido, apart from - huh? Passively sitting and waiting to be attacked is something we train in for the first couple of years of learning aikido, but after that we should really be moving to a more proactive approach. Look at O'sensei's original training manual: In the explanations the first step always comes from Tori (admittedly, that first step is sometimes "Tori fills their body with ki and invites uke to attack" - but its not passive, and fewer than half the techniques listed there).
(a different) Tim