I was in a guild that had a point system for active members. You got points by going to meetings, donations, teaching classes/running projects, work parties, working the yearly show, etc. Then you could spend your points (auction style) for highly desired retreats or classes. Newer/less active members might feel left out, but the more active people might spend like 20 points (and clear out their total) to make sure they got into the retreat, while other people may be able to get in with only 3 points. I think it is a good idea to have limited number of possible points, sort of like work vacation use it or lose it policies.
Of course, this would require a change in by-laws, reminders, and someone to assign point values and keep track. We had a spreadsheet that was viewable by all and listed names and points. Once set up, it wasn't too bad to maintain, we had sign in sheets at the official point scoring events.