I'm pretty sure an idea similar to this was brought up in another thread, and the biggest argument against it was that it would divide up an already small community even smaller. A compromise that came up included blurring the edges (ie: 1-5, 3-7, 5-9, 7+).
Although I'm fairly certain the upcoming matchmaking system will replace the match sorting list we have now. I know they talked about it at the last fireside chat, and I'd be surprised if it didn't come up again this time around.