18x10 has been done, but is aggressive. Certainly possible that fender liner modification or camber change may be needed. 265/35R18 or 275/35R18 tires.
For comparison, the 18x10 wheels I sell are ET25.
I have accepted a new position at Tire Rack and am no longer in the sales department. email@example.com
is available to assist with M3 questions.