Many BMW's share the same parts as the M division (steering wheels, seats, etc.)
It's ok to have PARTS that have the M logo. However, is is NOT ok to put the actual M logo on the outside of the car to rebrand it.
"So what does it take to be legit Msport?"
It takes the purchase of an actual M car.
However, at the end of the day, it's your car, do what you want with it.