You mean the method we tried before but had authors bite our heads off over it? That one? The one where they didn't understand that once they upload a map, Bungie/343 had the rights to use it?
It was tried. It mostly ended up with either the author never responds, wants in a playlist that we can't submit to, or the community wanted their own entire freaking playlist to themselves for the maps to be in matchmaking. Or they don't respond, got a map in, and then bitch that a small change was made to make it MM compatible. A few in MM to this day were gotten this way, though, and weren't submitted by the author.
There's something new in the pipeline to improve the process, but having authors that actually want to be active with their map resulted in more content being put through the pipeline.