Remove Season Rewards
That is, except for the border and icon.
That would remove most of the incentive for players to cheat-- yes, smurfing with a diamond buddy is cheating even if it's technically allowed by the rules for the sole reason that Riot can't track it.
If all you get is the icon and border, there'd be little reason for someone to boost themselves up in rank unless they actually WANT to play against people who will be so much better than them that they hate the game.
We don't need to remove dynamic queue, we only need to remove the incentive to cheat with it.