It is also possible that our understanding of zanshin was backwards all along. Rather, once we learn IP, we learn maybe our zanshin needs to draw more from our IP than our IP from what we may have mistakenly thought was our zanshin.
Yep, that's going in the right direction.
Awareness begins -of ourselves- from within ourselves. In other words, when we work "internally," we have to become intensely aware of everything that we are doing "inside," and the effects it has on us. We also have to be aware of our immediate environment as that is what our physical bodies are dealing with - gravity, our spatial relationship to our surroundings, etc.
It's like concentric circles of awareness radiating outward, but starting from within us. The whole process of learning to cultivate IP and aiki heightens our awareness of ourselves and our environment; you can't be a closed vessel. Once we're aware of ourselves, we then work on awareness of and sensitivity toward the opponent and his processes. Then we can learn to use our internal manipulate both the intent and body of another, and even learn to read someone's intentions before they have initiated any actions.