This, plus a penalty on number of years. Fail either and you get hit. 50 games in 4 years triggers it, but so does 40 games in 20 years to stop your ten year interval problem.Perhaps a sliding cut off based on the frequency of games in an era; say, starting at 50 innings for the old timers, and going up to 100 innings for the present.
Is the penalty fixed or does it scale according to the extent you fail by?