I'm no expert - in fact I'm a new quilter, but I've fallen in love with the dissapearing 9-patch pattern and I'm currently working on 2 of them. One of them is fairly uniform, with a limited number of fabrics and with standard 2-colour 9-patch blocks, cut up.
The other one is a mini-quilt (for my quilt guild's challenge) which I made from nine different charm squares, to make a single 9-patch.
I like the one with 9 diferent fabrics *much* better, and that's how I'm going to do them from now on.
So my vote is - go ahead and make a scrappy 9-patch - I bet it will look beautiful!
Jan