Love it. I think what makes the outfit work is that plaids, even though they are mostly the same scale, do not immediately overlap, there is always something in between: there's the tie (striped) followed by a plain shirt followed by the scarf and the vest (both plain) and then the jacket and overcoat, which are themselves separated, again, by the scarf. It is a bold look, to be sure, but he pulls it off. I would use a heavier shoe to anchor the look