So you agree with what I said about limitations of this technique.
I know it’s not ideal. This is just experiments while I’m discovering UE4.
However, I think a postprocess material is not the better way to achieve such effects. It would be better to use shaders. But, as already said, I don’t know how to do it.
Or it would be cool to be able to manipulate camera layers but it seems this feature is missing in UE4.
The problem in your gif is that I see blur nowhere. The effect is cool but where’s the blur? Must be a subtle effect.