Everytime I see a pic set up like those three (especially the last one) I think BEAST! They look so mean. I like your idea with two seats that can be swapped out. That last pic is almost like a mix between the two. You could always run something like that with a smaller "bump".
If I do end up making a cafe seat, it will be a fiberglass bump. As of right now, I'm not into the leather covered bump.
I agree that last bike is a beast. When I was looking for my bike I wanted something very narrow, so I went with a twin. After seeing that bike, there might be a 4 cylider bike in my future.
