do you think Yzerman's vision is 100% out of that left eye? and even if it is, see Berard, Bryan. sticks and pucks get up both accidentally and on purpose all the time. it's just not worth it, especially if you're not getting paid to play.Stevie Y still has both eyes.
Not allowing beer league punks to hide behind a cage would bring the temperature of the game down.
I can't speak for your league but my local league doesn't have these "punk" problems. most likely because when issues do arise we come down pretty hard on the offenders. the head-butting discussed a few posts ago would earn a match penalty and hearing before the league's board.
part of that might be because we are an independent league operated and run by the players rather than the rinks so we're not afraid to toss players out for life. their money will be replaced by someone else's in a matter of days.