The calipers only? Or the calipers, rotors, pads, lines, and brackets?
Part of the reason you get a BBK is that the consumables are cheaper and last longer. So for looks...you want to saddle yourself with a system that saddles you with even more expensive consumables? You'll spend more on getting a bracket machined.
Sorry...this is a dumb idea. Why not just get some BBK calipers painted or powdercoated?
2013 F30 328i Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red