Remove everybody's blue/white names now, and right before the end of every playoff. You gotta place top 64/32/8/3/whatever to keep your name each season. That way people will be motivated to do the ladder every season to keep their status.  Winner of each playoffs gets to keep his special color forever though.

And if you want to have extra encouragement, make an "elite freeplay" chat that only people who made the playoffs last season could join. That way they can always find players closer to their skill when they want to get some wifi training.  (As a reward for making the playoffs, not as a punishment for everyone else for being a scrub)