We are always learning along a continuum - in any dojo there will be people who cannot throw me and people I cannot throw. So yeah, with a newbie, I actually keep my idealized ukemi a step ahead of their nagewaza and not only fall for them, but guide them through my body. Past that, my willingness to allow myself to be moved is based on starting the first time as uke with total cooperation, attacking to their center and then essentially allowing nage to lead as long as she has found some kind of connection to me (the kind being related to a sense of her skill level) and letting myself follow where her leading is taking me. If she disconnects I let her know and let her refind it rather than start over. With peers and seniors of course I expect more and don't simply follow nor do I resist statically if they mess up, but gently ramp up my own attack on their center to give feedback that can be used to self-correct.
I don't see my interactions at the dojo as "winning."
FWIW, there were a couple of dojos I was a member of that were not paragons of cooperation. They also were nothing about what you would call "aiki" - they were purely into the mechanics of imposing the asked for technique with lots of muscle power regardless of the form of uke's attack. So I don't have a very high opinion of non-cooperative training.
However my view is that within cooperation there can be, and should be, the contract between partners to test one's limits.
I believe it is Chuck Clark whose teaching is based on the principle that one should succeed 90% of the time in order to learn. I think this is true, whether the partner practice is slow and aiming for feeling connection or faster and working on the form of a specific technique - it is in the 10% failure that one learns what is needed in order to progress and in the 90% success that one starts building the incremental muscle memory (for lack of a better term) that drills the skill in.
I think part of the problem may be semantic. Bear w/ me for a moment on this: I have felt/seen two very different kinds of aikido, as have many of us: the "wow that was a strong throw that sent me across the dojo" and the "wow how the heck did I end up here". I think for many of us the goal is the more elusive, harder to find latter feeling.
I think we're saying essentially the same thing. Testing in a cooperative manner as a means to grow. Actually I think most people in all forms of Budo practice and think that way. It was how most of us learned. The differences seem to be where we go -from- there.
Do we stress test? This can some into play in any art.
Stress test #1:
So if we leave Ki or Aiki out of the equation, it becomes a question of how much stress or what are our goals in learning self defense or to fight. The levels of ukemi etc. Those goals are fairly straight forward, those debates have been had, and many have found their own solutions.
Stress test #2
With IP/aiki we have the same questions to ask. How much stress, when to we up it, and against who? I see it as a very straight forward model that fits into Aikido and any other art very well.
So when you write of "center driven power to a level where few can stop you?" I have a feeling that however you may mean it, for many on Aikiweb this smacks of the style of aikido they have experienced (as I did in dojos like the couple I used to train at a long time ago) and are not interested in doing.
The culmination of attaining a level of power where few can stop you does not have to be a power play though is it? And it very much can lead and does lead to the "How the heck did that happen?" feeling. You know...the kind that leaves a smile on your face. That is the goal that most I know who pursue this work are finding fun and even amusing. I don't think anyone is seeing it as a sort of bully boy attitude. I know I don't. I see it as a heck of a lot of fun, and intriguing mind game and physical challenge that is very relaxing and mentally taxing.
I think walking away with a smile on our faces, and even laughing out loud while doing it beings a different definition to power.
I'll try to find it but a YiQuan teacher mentions much the same thing that Tohei did. THat when you practice this way and the opponent feel himself sent away, it leaves a look of surprise and wonder on their faces.
It sort of makes Ueshiba's model of making peace out of an enemy come to life again.