By the way I did some research into 3D printed footwear for a business last year, with this article summing up some basic findings:
https://designsoulblog.wordpress.com/2017/09/02/3d-printing-footwear/
Did you know you can improve interlayer adhesion by creating layer patterns that do not move only on the XY plane but also shift in Z direction while printing? That makes 3D printing more towards truly 3D homogeneity and will improve the bond. You will need some scripting ability but Rooie Joris made a good start.
This would be one of the end possibilities:
