But I do have a question for you- I was wondering why you suggest that there is a need to feel the load you are supporting in the dantien. I may have misinterpreted what you are saying, but your post seems to suggest a hierarchy of desirable load-bearing structures, with feet being the most basic, then kua as more advanced, then dantien. I always thought of dantien as more of a focal point for initiating movement that was primarily supported/driven by the ground, via the feet.
when you roll on the ground, the ground path doesn't always toward your legs. often it goes through the other person if you are on top or through your back if you are at the bottom or through your own arms. so using your middle as the control, from my point of view, would be better. but that's just me.