I did this once with a quilt top that took me six years to figure out what was wrong , the last border was the wrong color and made the quilt go flat in my minds eye. That is what I finally took off and changed. Then finishing the quilt went off like a dream!
My suggestion is to find a floral print with the colors that are in the middle blocks and border it with that. The scallops could still be used and would be a beautiful ending.