I don't think it looks stupid, but I drive a baby blue/orange Mini.
The seat swap is not stock/street-legal unless you do both and they are so similar to the FoST Recaros as to be hard to distinguish, though I doubt anyone will notice or care locally. Since a harness is legal in Street, I don't see the "competitive advantage" argument holding water, but I'd be hesitant to show up to a Pro or Tour with mismatched seats.