It just wouldn't work, because you still have to fit a tire between the stays. You can make them as wide as you want at the bottom bracket shell, but they have to become narrow enough to fit a tire about 2 inches away from the shell. That "laterally stiff and vertically compliant" stuff is mostly marketing BS. You can make the chainstays as compliant as you want, but they can't move in the vertical plane once you attach the seat stays. A triangle is just not a flexible structure.