Shouldn't limit a system like this just to the weekend, where some players may not have time to play. There are some "casual" players who may hop on for small amounts of time during periods where player count is low. Having a double xp modifier would motivate them to go make their playtime worth it whilst the event lasts, instead of just hopping off and waiting for more people to join or just going to play a different game, This would be a great way to thin out or even eliminate dead periods where player count goes down.
oh yeah, Support