Over the years, many people said they were going to make a downpipe using an integrated elbow. I don't think that is possible. If you take a look at the picture, you'll see the elbow is held on by four bolts - one of which is inside the elbow itself. That would be tricky to work around.
I wouldnt see any advantage to making an intergrated elbow. it hasnt been proven that the factory piece is a restriction and if it is, the compressor will long run out of breath before it would be an issue.