>I guess if you use it as a "wind tunic" then maybe it is versatile as a wind layer, but how is it "more" versatile?
it is more versatile in the sense that supplex allows you to remain comfortable in extremely wide range of condition. This is my go to clothing in summer. It is cooler then wearing shorts plus a shirt because of the amazing ventilation. I have worn this on glaciers and upto 18000 feet during my expedition in june. A single layer kept me warm and cool most of the time so I never sweated much. On summit day I was warm with just a thin fleece Inside. Which is just fantastic. We had a snow storm and and supplex worked very well. I did treat it with DWR.
>How would a longer wind layer be more versatile?
Once you put on your harness, it is difficult to remove layers from your leg if it get warm. Long wind layer allows greater flexibility. On my expededition I didn't carry any wind pants but my leg stayed warm.
>What do you do for a rain shell? Where I live going without a rain layer would be suicide in all but the hottest weather, when getting wet isn't dangerous.
In monsoon I just get wet which keeps me cool. I havent hiked in freezing rain but if I did I would make something similar to roger's silnylon mountain poncho.