As it is, the system set up for events is not well polished. Trapping people in the hub where there is nothing to do is just not a good idea. I'm sure you've been trying to do something about this, but I thought I'd try to say something. It's entirely possible that the suggestions I bring up are impossible to execute because I don't have too much knowledge when it comes to developing a Minecraft server. I think that the best way to have a queue would be to put it on the invaded lands website. When it is time to do an event, you run whatever command is programmed to consult the online queue. That command attempts to tp the ign's of the first 100 people into the event server. If the tp doesn't go through because they aren't on the server, it just moves down to the next name on the list. To actually okay an entry into the queue, it should send a message into the person in-game to confirm and there should only be a certain allowance of entries per IP per day. Maybe 2 or 3. To make sure the queue doesn't have too many afk's, just reset it after every event. A system like this would allow for people to use their Minecraft for other purposes or play in different parts of the server up until it is close to the time for an event to start. It may also be a good idea to post the times that you will be hosting events. Again, I am not sure how possible any of this is to implement, but I hope that someone takes the time to read this