It's no different than LTBWM's F10 to M5 conversion. It's your car, do what you like. They didn't make a lot of 1Ms so it's not that easy to "just get a 1M". I agree, it needs a rear conversion or it looks funny.
JB4:Injen:NPG DP/Exhaust:BSH OCC:BTIC:Alpine:Icarbon:
Turbosmart:ER:KW V1:VMR 710:Nitto.......and METH