Very unusual quilt. I liked Dunster's so much I ordered the book the pattern is in.
If you are wanting the quilt larger, I would think about adding a dark green or one of the other darker colors in the quilt as a stopper border (1" or less), then add the 3 borders you are considering (making the print fabric wider), then go to a last border the same as whatever you chose for the stopper border. By adding so much light colors at the edge of the quilt, you may lose your impact for the gorgeous piecing you did in the center.
This pattern is at the top of my to do list. I love the effect and not having to deal with bias edges is a big plus.