Don't think for a minute that it won't work because a tiny model (different style altogether - one prop in the water and another on the same angled shaft was a fan blade in the wind) was written up in Scientific American on their amateur page many years ago. Mechanically, it is quite sound ... just don't stand up at the wrong time ;o)
Here, the red and green "sails" flap open when heading into the wind and collapse the other way, i.e. they catch the wind like an anemometer and deliver the wind generated rotation to the transmission where the two opposite spin shafts (one within the other) drive the same prop. You install a clutch with forward & reverse and maybe a high & low gear ... hah! [Oh, and don't forget a rudder - not shown]
Now, you can go in any direction with the slightest breeze and no leaning so you can have a shallow draft for ponds and docking in low water. (It will lean a bit but the "sails" are made low down so that there isn't much leverage. Just watch your head as the sails rotate.)
Top view (one sail):
This might make for a great deal of flapping noise. The alternative is to "fix" the sails as in an anemometer but this would reduce efficiency ... which is what we really need in a very small hobby craft.
If anyone has seen something like this in action ... let me know and-or send me some pics.