Dan, it can be done prior to Aikido. It would be very useful. However it cannot be done whilst moving or whilst doing Aikido.
Of course it can. Easily. We can learn techniques for observing many things. Observing tension in the body - but with no judgement. Observing tension and "being" tense are quite different. Being tense is an unconscious state. Observing tension, without judging it, is a conscious, non-resistant state.
Observing the execution of a kote gaeshi technique. Observing it. Not "doing" it. Observing rhythm. Observing timing. No judgement, and no particular focus. Just observing the process and what the process contains as it arises.
Observing the cold on our hands with no judgement is quite different from "being" cold or "experiencing" cold.
This also allows our aikido practice to take place on a very different playing field. We can become conscious witnesses to our training. This is not mediation, and it's not contemplation. It is a technique for unfettered observation and discovery of phenomenon within our practice. And when we do that, we increase the resolution of conscious awareness within our practice exponentially.