From what I've seen, on the Cooper the front plate bracket is moulded into that panel. That is to say, there is a removeable panel in the bumper (fascia) that can have several different license plate types affixed to it, depending on the market. My state requires a front plate, so the panel is moulded to integrate the front US plate. It is color matched and, as these awful things go, as good as you could reasonably hope for.
If you opt to go for no front plate in a state where its required, you're going to need to somehow acquire the non-plate panel, otherwise you'll have a big, blank flat spot out front, drawing attention to where your plate *should* be. I imagine in states where no plate is required they'll come w/ the 'normal' panel.
On the S, however, it is not a moulded/color matched bit, but rather a more conventional black plastic plate mounting bracket that affixes unbecomingly to the fascia. On the S it will be a simple matter of removing it.
Personally I'm going to ask my dealer to not touch it and "let me put the plate on," hopefully avoiding any holes in the plastic.