G'day Paul,
Easily the most used shelter shed that I ever saw was something like that, just a long, wide flat roof with a solid 'copper log' thickness pole on each corner...basically a large rectangle that was wide open on all sides, but there wasn't any prevailing wind there that I can recall.
They seemed to use it a lot more in the summer to get out of the direct sun than they did in the winter to get out of the bad weather/wind/rain.
Maybe knock up a shelter like that and have a detachable wall which you could move to one side or the other depending on the time of year and the prevailing wind?
You could even go up market a bit & make it look really flash with shiney brass wingnuts to hold it all in place. The sky's the limit.