I love the idea of a denim jacket and paired with one of the skirts you make it would be adorable! I think you covered the only concern that came to mind, being the softness of the material. I've bought Lucy some really nice jackets and they are so stiff that she just stands there like a statue in them...lol.
So, my honest opinion is that they are great and I would buy one! I'd wash it tons so it breaks in like my own denim jacket