The nose of the saddle is essential for cycling at some speed, because you don't want to have to turn the handlebars to turn.

I wonder whether someone could train to steer the bike with only the hips, no upper thighs.... but I strongly doubt this will appear in cycle racing any time soon!

This being said, on a comfort bike where you're totally upright, it might do a lot of good!! I'm sure some roadies have tried it too.