If you don't put any batting it will be a very lightweight blanket. This kind of blanket is easy to find in stores, but not a more heavy weight like a traditionnal quilt with cotton batting. It makes a more unique gift. It's so useful for playmat, tummy time, carseat, etc. Also, it make a wonderful lovey blanket for a toddler. Cotton become very soft and souple after a few washing cycle.
Don't forget to use a good quality flannel. Prewashing it is for me a good way to check the pilling. It happen once in a while that I decide to not use a fabric because the pilling is too bad (this fabric end up in batting or pyjama instead)