I don't know what your manufacturing or fund capabilities are, but what i would like to see above all else, is a tightly and simply woven, non grid stop, windjacket made out of Ultra High Molecular Weight Polyethylene fiber (dyneema and spectra are brand names of this fiber). CFM of about 25--being tightly and simply woven with no grid stop, and so hydrophobic should be highly water resistant.
I did some research into it once, and found that there are plenty of Chinese companies that make this kind of fiber and yarn for much cheaper than you can get in comparison from sourcing from DSM (dyneema) or Honeywell (spectra). But, you have to buy it in bulk, then you would have to have it woven into a fabric--an expensive venture.
I know, it's a lonnnnng shot. A UHMWPE fiber based windjacket would be a wet dream come true. I'm getting all hot and bothered just thinking about it. Ok, no i'm not, but it would be pretty cool. It would be so UL AND at the same time ultra durable--might last longer than me. I'm totally ok with the color white.