i would prefer to see a ranged attack that can actually kill people (sure, his teleport skill owns mobs but it's definatly short when it comes to killing champions).
What i would do, is a attack that can only be triggered after activating his Ultimate.
I would make it a vertical swing, with the range of his teleport ability (or slightly bigger). Using this ability would then prevent the instant recharge if you kill a champion with it.
Damage should be 300-500-700 to each level, the AoE is very narrow, but goes through everything in it's path.
It would make him more fun to play. He doesnt need it though (Yi is my main champion), would be cool to have more active skills instead of the "i win" buttons.