Dont really like the event key idea, I would prefer instead that people who attempt to join events but fail to do so get an automatic higher priority but not a "key". For example lets say theres an event, you barely missed it, but you already missed a previous event, so you have priority and theres a 33% you replace someone without priority in getting into the event before it starts. Now lets say everyone who joined an event has 3 priority which means they had 99% chance of getting in, well now someone with 4 priority tried to join, they have a 32% of kicking someone off the list filled with 3 priority players and so on.