I'm a free form type of gal and don't use any type blocks. I just take scraps and start sewing and make it as large as I want to.
At least that is how I did the first three tops.
Now I still free form sew pieces of fabrics together and than take my Go and Studio dies and cut those into shapes like squares, rectangles and such to create yet another one of a kind type quilt, rag quilt, whatever.
I've been more successful with it than I ever thought I would so much so that I've been asked to teach a class on it with two different guilds in the area.
I see alot of folks do what you are thinking of doing and they also turn out wonderful scrappy's. I think there can be no such thing as a bad looking scrappy no matter how you decide to do it.