When I saw this topic I remembered a footwear brand I came across a few years ago called ‘Skins’. Essentially the upper and outsole are one piece (this is the Skin) and then there looks to be a TPU mould which goes into the shoe to give it structure which they call the Bones. The whole idea is so you can interchange your shoe (Skin) depending on where you are and what you’re doing without changing the fit and feel (Bones). I’ve never seen these in person and had completely forgot about them until now. Here is the link anyway http://skinsfootwear.ca/index.php