Riot has an extremely easy way to deal with massive amounts of smurfs.

REQUIRE email verification. No one should really have more than 3 emails (business, pleasure, spam), and no one wants to go through the difficulty of making a new email just to smurf on some... game. So, not only do you reduce the smurfs by a shitload, you improve the game in every way, and everyone who has already verified their account has nothing to worry about.

But then again, the playerbase will drop from like 25 million to 6 million.