200 feels artificial. Over time the meaning of "200" has changed as the number of potential voters has increased.
Maybe something like this. At the beginning of the year, look ar the rep of the 10 hignest nodes that were posted in the previous year and use the lowest score of that top 10 as the cut-off point.
And further it would be nice to be able to go back and look at the Hall of Fame at any given week in the past.
Would be nice, but I'm afraid rather impossible with the current database setup, as that doesn't keep when votes were given (as far as I know).