Is your service advisor a prick.....
Most dealerships wont give a crap if the paint is done nicely, but the long and short of it, it will void motorplan, even if you use original bumpers.
If you bought the bumpers new, had it fitted by an ARC, then you could maybe get away with it, but trust me when I say you do not have that kind of money, or will be willing to part with that kind of money.
Most service advisors will overlook it/not even notice if its done well, but tomorrow your motor pops, bmw opens up a puma case, they come out to inspect the vehicle, and motorplan goes bye bye...
Oh and on motorplan transfers, if the guy is semi awake, and picks it up, lets just say life's gonna suck some more...