OK I have still been following this thread to see what you decide for the border. If it helps, and I hope my opinion does not hurt your feelings, I would not like your piano key idea for the border. There is just so much movement in this quilt that I think that type of border would stop all the movement.
I personally agree with the dark border and binding, this would allow the quilt top to continue to flow, kind of like the stars in the sky comment.
Whatever you decide please post your finished quilt I look forward to seeing it.