Well, I've built more than a few motors in my day (and killed a lot of transmissions).
So I'll put in here. Back in the late 80's (I think) Buick tried replacing the valves with solenoids. What they discovered was that by yanking the valves open all of a sudden, they lost all semblance of vacuum. The mixture literally didn't know which way to flow. THere has to be some sort of curve to the valve opening rate, I don't think anybody actually knows why, but the same thing happens as your cam lobes get more "square" in shape. Low end power (less than 4000 rpm) just goes in the toilet.
As to parasitic losses by the valve train, its highly over rated. Famous Nascar guru Smokey Yunick once built a motor that used needle bearings throughout. Crank, rods, cam...everything. The idea was to pick up lost horsepower from the supposedly inefficient insert type bearings. It quadrupled the cost of the engine and they picked up less than 5 horsepower.
BMW does some kind of electronic control of the valves and does away with the throttle. I don't have any personal experience with it, and don't intend to. It sounds like a breakdown looking for a time to happen and bear to troubleshoot when it does.
