What a cool idea! Sure it would work, why not. I like the idea of cutting them into 9" squares. You could add nice white cotton trim around some of the square or as a border. You could also do nice silk ribbon embroidery in the squares, like pink roses.
I love the idea. I am going to ask my daughter-in-law to start saving the jeans from my 3 grandsons, herself and my son. I would love to make a quilt with that.