Hey zingaro - I have photos somewhere of me doing that too. It is really fun and handy if you need a little "relief".
You can actually do the same thing just hanging onto your tiller extension and using your feet to steer your body and thus the boat. I never hooked up with the diaper or bucket though.
There may be a drawback though....My better half reminds me of the time I was doing this and things got a little out of hand as I approached shore one evening. I had miscalculated the power and speed that I was about to be treated to by the evening-onshore breeze. The pressure of the water pulled my baggies from my waist down to my feet.
Pulling them back up was not an option since I was unable to hold the tiller extension with one hand and pull them up with the other. While trying to do that I lost contact with the mainsheet. I tried like crazy to hang onto my suit with my toes as I felt it ever so slowly slipping away a bit at a time and eventually I was being towed into shore, buck-naked, behind my boat.
Luckily our beach is all shale and I was able to land the boat, but of course unable to do anything but sit in the shallow water until someone would bring me a new bathing suit.
As I recall, the help I needed was a LITTLE less than forthcoming as I endured taunts of the hysterical crowd on shore who were happy to get me a beer but not any clothing.
So, as I said, don't do THAT!