Basically, have a Burning Man type of event in SAES, once a year. Where you and your group of friends can claim a piece of land throughout San Andreas, and use the panel within that land freely to create whatever you want. Art installations, party zone, custom type of events, services, for example car fixing, refuel, letting people try new cars/planes. Anything you can think of, 24 hours of blissful anarchy. Able to change skins, mod cars for free. The server will be saved before the event starts, and after it finishes, it reverts to the backup, so no traces of the event are left.
I think such an event will be amazing, keep the roads clean and allow creative outburst. People will visit one another and enjoy the fruits of creativity and make new friends. Groups or individuals can prepare for the event and make it unique each year. Exploring San Andreas will never feel the same again.
Edit: Losing a day would not be good for gangs and squads going for levels or trying to meet requirments, etc. Maybe a special area, that can be warped to. So that it doesn't interfere with normal day-to-day activities.
To understand what the fuck I am on about, this is Burning Man, please watch/skip-through the following videos, you'll be pleasently surprised: