Your right, 52021 is probably less than useless for front end protection. But it is the most beneficial part of the entire bumper when it comes to performance.
It's a large drop in weight, and its at the very front of the car so it really helps turn in performance when swapped with the old heavy steel crash bar.
It isn't required to support the bumper cover - the cover doesn't bolt to it in any way. You can make your own out of alumium or steel if you like. Check out Dudeman's project thread for pictures of his custom crash bar.
You don't need the bumper cover clip strips which secure the cover edges to the fender. You can use your old ones by drilling out the rivets and transferring the strips over to the RC cover. Just needs new rivets.