I wouldn't import it. Getting it reconfigured to meet federal and state regulations, while doable, will cost you money and a great deal of agrevation.
However, if you are only going to have the car here for one year or less I believe you can bring it in as-is keeping your MOT registration. You will have to certify and subsequently prove the vehicle was exported by the of that year. This is all from vague memory but it might be your compromise solution. Who knows, you may not like living here.
2010 BMW M3 Coupe M-DCT w/Tech-EDC, BMW M Performance Exhaust, BPM: Stage I / Euro MDM / DCT / Steering, Space Gray / Fox Red Extended, and a Trunk Monkey known as "Der Stig", plus the daily driver...
2011 BMW 135i M Sport DCT, w/BMW Performance Power Kit, Exhaust, and Brake Rotors, Space Gray / Coral Red, known as "Stiggie" with an outlaw F20 "M135i" badge.