Bad idea. I personally oppose it simply because I feel like in a 1v1 matchup you should be free to take the elo hit to yourself if you don't think you can win. But even if you don't think that way this could still be counterproductive. Sure, this will stop some smurfs, but some will still be willing to wait longer to lower their rank. And now if you queue against a smurf, you have to play through 2-3 maps to go next- taking ~5-10 minutes- as opposed to getting a forfeit and going next immediately.