my vote would be for 10 of 13 games to count for season standings: 10/13=76.9%, 9/13=69.2%, 8/13=61.5%. so i would vote for 10 as it is closest to 75%.
actually, i think it should be the whole standings each season that counts. if you want to win the nascar championship you run every race, if you want to win the nba championship you play every game, if you want to go to heaven you attend church every week, or else you accept a lower overall standing than those who prepared and competed consistently.
with only 12 members and 8-9 regulars playing any given night, i don't think it would matter too for attendance much if the number was 1 or 13 games to count, if folks want to play and have time to play then they will enjoy the games they play. if they want to compete for championship prizes they will compete regularly. as far as metrics go, there is always the 'lifetime' standings, and it would not be difficult to average out a player's performance (% of games played won 2nd or 3rd etc., number of points/game played, or whathaveyou to establish a player baseline).
i don't understand the "protect the working men and women" theory and "make things fair" attempt. the poker table is the great leveler, it is a fair game and needs no additional "fairness" or "accomodation" built in, it solves itself in a perfect solution every night. presumably we are all alive and have lives with other commitments besides poker, whether that be family or karaoke or some computer alogrythm lovin. again, if it is important to play and compete, one finds time to train and attend competitions and compete.
i think 3 'gimmes' out of 13 is more than enough to allow for important or unavoidable events or required travel or whatever. any more than that and it becomes less of a pure competition and more of a hippie commune where everybody eats the same potatoes regardless of production. poker is the opposite of communism, sieze the day if you want it, if not be a happy hippie and live every moment of the games you do play.
my vote is for 10 games per 13 game season or 75%.