BMW should have just put the old DOHC 3.5 liter from the E34 M-5 (the most desirable modern BMW in my opinion, having the E34 body style and the classic Big Six tuned to a fare-thee-well) into production again. Sure, the 3.5 DOHC made "only" 320 hp, but it would have probably had more usable torque than the 3.2 liter M3 engine. Car probably would have been just as fast, and the 3.5 liter DOHC hit its rev limiter at 7,200, giving lots less internal stress on the engine.

-Sam