Hey Pupeno.
I am new here as well. I like your thoughts on this. I remember early on, Sensei once used me for a demonstration - I was one of the largest students in the class. Anyway, he asked me to attack him. I replied, "How?" He responded with "Anyway you choose."
I attacked, but it wasn't whole hearted. He easily floored me. Then he asked me to attack with sincerity. I did. I was rewarded with some serious lessons in "blending" with the mat!
At one point I decided that it was not even worth the effor to try and stand, so I attacked from the ground. He wrapped me up so quickly, had I been in kumite, I would have been in serious trouble. However, He never inflicted any damage on me and never once lost his composure.
I am 6'4" and weigh about 220lbs and am by no means slow or incapable. He was about 5'6" and around 144 lbs by my guestimation. I learned alot that day.
Peace.