Something occured to me while reading your post (thanks!):
An idea could possibly be to add some of the fun customization options to International Ragnarok Online (IRO),
Classic and Renewal would be great, that pservers offer - that way when advertised as having customs, people would
definately choose our servers, since the population is solid and established.
I remember back in the day on a pserver far far away, one of the fun options would have been custom dyes.
There we're so many to choose from it was awesome! I think I had a Paladin all in white or something.
I fancied the idea of being a Knight in shining armor, and the game made it possible to do so.
Another cool little feature I remember was the ability to duel other characters in town (both had to agree first of course)
but it was a subject of conversation and a way to test yourself against a friend - the option to agree/decline was interesting.
I understand you have more creative control over the Classic server, so maybe at the very least this could be done there.
Along with other customizations that don't affect the game in game changing ways.
That would certainly be an incentive for me to play Classic, but some changes of the like to Renewal would be super too!