Re: Shu Ha Ri
I think the potential for "ha" (break the form) can emerge as early as nikkyu or ikkyu, as soon as kihon waza are solid enough for the perception of suki to occur. As the student begins to perceive openings in nage's and uke's movement, the idea of adapting kihon waza to the immediate situation can occur.
This would not be an appropriate time to concentrate on this aspect of training, however. Levels of skill for rank vary so much among various organizations that it is difficult to name a rank at which "ha" would become a larger part of training. My intuitive response, based on my own training, is Sandan. By this time kihon waza should be well integrated. In addition, teaching is a great stimulus to explore larger and deeper aspects of Aikido.
It seems to me that personality would play a large part in this evolution, as it requires a creative leap and a high tolerance for uncertainty. My experience is of technique falling apart for months at a time as I work to integrate new insights.
Thought provoking question ....
$.02 from Sharon