To me, you are talking about doing Aikido instead of just practicing technique, which is a pet peeve of mine. I agree with you, although I have a slightly different view of it.
At the basic levels, practicing a specific technique involves Uke giving the appropriate attack that warrants that specific response. If they give a different kind or quality of attack, doing the prescribed technique would (likely) be, as you say, going against them. Expanding one's scope of practice, one would respond with what is appropriate to whatever Uke is presenting. I whole-heartedly support this. This is training to do Aikido, and I don't really see a whole lot of it.
I think too much Aikido practice is not actually Aikido per se, but simply learning and practicing a particular way of executing techniques. Some people never move beyond this, no matter how dynamic and dramatic their "Aikido" appears to be. I completely agree with you when you describe these constructs as "confining shells", "prison cells", and "straight jackets."
The interesting thing to me is, in a sense, that applies when one is perceiving "what Uke is giving" as what they are physically or even energetically constellating. If we look deeper into their being, at another level there is only one thing that they are presenting, ever: themselves, in whatever dynamic form that is being expressed. At that level, if we tune into that, or "them" as it were, then in theory (and practice), in that moment any number of techniques can be applied, beyond just what they are "informing us of" through their physicality, intention, etc.
This takes a deep technical knowledge and skill, but also deep perceptive skills that reach into the energetic and qualitative levels of connection, intention, balance, and manifestation. In those moments, my experience is that, while in truth "form follows function", one can apply almost "any form." This does have it's limits, ultimately defined by the same criteria - what Uke is "presenting", just at a very different and perhaps a more "open" level.
The other important point I would bring up is, learning to go with the flow is ultimately of most value, but I don't think most people can fully learn Aikido and have free access to consistent skill without a balance, and that to me is the answer - balance - between form and essence, content and process, technique and flowing creative response/Aiki.
Similar to playing an instrument, one can learn to solo, really fly with the music, but without having a solid, basic relationship to the instrument and to music itself, the ability to do so is transitory, not grounded, and therefore missing the elements that sustain a deep evolution and knowledge over time.
I personally believe in inducting a student into both realities, which when done carefully and consciously, can help bring someone along in their training (ability and understanding) quite quickly.
So, I actually both agree and disagree with you, on both the practical and theoretical levels.