My take on this subject is
If you do have the badge on the back, the car has to have some 'M' DNA in it, and be capable of putting its tail lights in front of most who test it out.
I think that the 125i M Sport and M 135i have that capability and do it affordably.
De-badge or add, it is a personal thing. If it makes you feel better about your ride 'DO IT'