Aiki is useless without the body being in balance as all three of your videos show how one person maintains their balance and the other loses theirs.
I am not sure where to go with this...
Yes, aiki is useless in any number of situations. Somewhere along the way, aiki=superhuman powers. I don't know who made that up. I am pretty sure there are plenty of aikido people (who don't have aiki) who are plenty well balanced, and still can't last 30 seconds against a good judoka; probably less time in MMA.
Yes, I suppose if you have someone practicing martial arts who is not balanced, she will may have a more difficult time throwing someone who is more balanced. Of course, if you have someone who can't manage the basics of her body (like balance) there is also less chance she is gonna learn the body mechanics of aiki, anyway...
No, I don't agree that someone who has aiki can't apply it while unbalanced. In fact, I know plenty of people who can apply aiki while in a period of balance transition. That's the problem, though. "Unbalancing" is a temporary state as the body transitions from stability to stability. Most people walk in a constant state of unbalance. So what? Why can't you apply aiki? If you get thrown, you have to be able to apply aiki to perform reversals. What about sutemi waza? Balance is a just relative position of your body.