I was already writing a comment about procedural generation before I saw yours. I was thinking about placing shapes on the boundary of a basic character shape,

I was already writing a comment about procedural generation before I saw yours. I was thinking about placing shapes on the boundary of a basic character shape, and placing random points within those shapes which then have lines/splines drawn between them. You could change the size of the shape depending on how much you want the shape to vary. That way you can still exercise control over what specific features are preserved. I'm sure someone can come up with something better.