Suggestion for membership requirement would be N (e.g. 12) hours of volunteering in the past year.
Volunteer time could include being at meetings / director's activities.
People should apply/sign up for initial membership, which would then continue as long as volunteer hours are kept up, and in the absence of resignation/removal.
The reason for requiring that people apply/sign up for membership is that many volunteers aren't interested in membership. Having too many 'inactive' members could cause paperwork/quorum problems.
The reason for a volunteer requirement is that it keeps people from randomly 'stacking' meetings (MEC, apparently, had this problem early in it's existence).