Actually, I have seen such a saddle. My dad, who is 94, still rides his bike. Recently, the prostate cancer condition that his Dr. has been watching worsened and his numbers got higher. He found on the web (believe it or not, he is the web Master of our family) a saddle that is just two kind of knobs that sit under the sit bones. This is what he uses now. He recently opted for a treatment that involves a lowering of testosterone and more estrogen (my menopausal sister said of his hot flashes 'welcome to my world') and this has worked wonders, his numbers are way down now. Anyway, he swears by the saddle thingie.
The bicycle is the most civilized conveyance known to man. Other forms of transport grow daily more nightmarish. Only the bicycle remains pure in heart. ~Iris Murdoch, The Red and the Green