I like your solution and I will probably replicate it myself. Thanks for the inspiration.
For reference, the Crocs Cleo model is, I think, the lightest off-the-shelf Crocs model. They don't attach securely so wouldn't be good for stream crossings. But they are a lot lighter than the other Crocs models, which I still see people carrying. They strap is hinged, so they lay pretty flat. And they don't have the gizmo between the toes, so you can wear them with socks. I've been using them on UK hikes where my feet are wet all day and I need a way to air out my toes to keep them from rotting.
My pair weighs 7.1 oz for the pair.
But now, thanks to your post, I'll probably make my own lighter solution.