I wish I had a water feature! Every time I mention a water feature, my husband harps about how much electricity it might take to run the pump all summer long.
Oh well, I don't fuss too much about it because he does so much other stuff. I don't know if our windmill would generate enough power to do a water feature, but that is an interesting thought.
I like your idea of having something at the base of the windmill. I don't have anything on mine, but some phlox, liatris, and daylilies grow nearby. I watch our windmill to see which way the wind is blowing too. It's a garden feature with function!