Just a quick thought, nothing to do with the RO series.

Someone mentioned Flyff. This is a free game with thousands of players, yet KSing and levelling isn't a problem. How?

Multiple channels.

This is basically splitting the server into multiple smaller ones. You keep your character and equips/level, but you have the option of which channel to play.

So players on channel 1, can't see or interact with players on channel 2. It's still the same server, same bandwidth, just effectively two smaller versions of the game.

This will make the game more enjoyable - less crowding, more monsters to go around, a slower-moving global, etc. Even the admins may like it as it splits the amount of moderation needed into smaller chunks.

I might expand on this later.