Get a better anti hacking system and make the server faster.
I agree with Jesse on much things, especially the one that tells that Gold players should get all waepons and Trial players can by them.
But the most important thing I think that should be done is this:
Close the server for +- a month and get much people working on it and make some great updates.
Then advertise for a release day ( host event and make it a great day.) I expeet that there will be much players on the realease day, and if its nice enough much players will stay at Zone and start to play it again.