Digging the exploration. Why not explore outside of athletic footwear?
Wood clogs are super popular among the culinary field… up front they are unbelievable uncomfortable, but as they wear then begin to shape a bit more to your feet. Most chefs are full of personalities (and tats) and on their feet for 10+ hours a day…that industry needs some serious design love.
I like the idea of using different shape and size triangles from Yo - Have you thought about a veneer? that would allow you a bit more versatility in shape.
Have fun with it!