I'll preface this by saying nothing magical happens when you hit a perfect 50/50. The car is only a few points off from the factory. Lowering the weight of the entire car still helps acceleration, braking, and cornering. I'm not even sure 50/50 is "perfect". I'd probably rather have slightly more weight over the drive wheels.
Hood isn't a bad option. It's also above the CoG of the car, so lowering its weight actually lowers the overall CoG of the car. That is a very practical option. Just swap it out and you're done, no real drawbacks.
You can remove the engine cover, and get an dual cone intake which will remove several pounds of plastic from the top of the engine. Small stuff, but it all counts.
ER has a front widebody kit that is available in dry carbon fiber that will shave a few pounds plus let you run wider tires in the front. It's pricey, but what do you expect? You shouldn't be worrying about 2-3% weight distribution if you aren't running 265-285mm front tires already.
I would not recommend replacing the factory crash beam in the front unless you have a purely race-only track car with a cage and whatnot. At that point, you can also remove the air conditioning, which is many pounds of aluminum, the pump, line, all the coolant, etc., and the stereo, and probably gut the dash, remove the airbag, and soforth.
In reality, something tells me the people who are worrying about weight balance in this thread don't have any other more worthwhile upgrades yet. You should get a wheel and tire package, a tune, M3 suspension upgrades, coilovers, etc. way before you try to make up that few percent of weight distribution up. Those will return you a much faster car for far less money that some obtuse goal of having a particular weight balance number.
2009 BMW 135i 6MT Sport, AFE intake, Cobb AP, Apex 18x8.5+9.5, 255/275 PSS