Make it so admins can toggle catchup exp so people are more likely to join a server in progress. For example if 3 people are logging 7 already make it so the next person going into logging levels logging faster. Make it scale it with amount of people and levels.
Another suggestion is catchup for stars gained the same way it works for exp.
All of this promotes people to join a server in progress which equals to servers dying out slower. (which is a pretty big issue)