I'd try blocking it -- ideally with steam -- and see if that can get it to lay flatter. Then I'd go with a poly batt if it's a wall quilt or a poly cotton blend if it's a bed quilt (unless it's a child's bed quilt in which case I'd go with Warm & Plush). My thinking is that a higher loft batting will help hide some of the piecing issues & then you'll have to be creative when quilting it, too.