I think having multiple shapes for stop signs would be a terrible idea. The red octagon is an international standard. Messing with it is just asking for trouble

I think having multiple shapes for stop signs would be a terrible idea. The red octagon is an international standard. Messing with it is just asking for trouble. The "4-way" signs are just an aid to drivers, to indicate what behavior they can expect from other drivers. They're not required, and no replacement for plain old good judgment.