That's a very wrong concept this days, "unique ideas", was 3-7 years ago, when L2 was at beginning and in its "flowering" time. Those days are gone. What we can have is recreate what we once loved and have the old school back again and enjoy it once again remembering the good moments we had back then. (That's my point of view)
I don't expect to resurrect 100% an old project, but based on what people loved we can build something better but in the same time stick to the point.
Not sure if anyone gets the idea, but i would defenetly play my fav server once again, and ofc i will be bored after a while, but i bet unique ideas will make me quit server even faster. That has already been proven. Unique ideas wont last this days anymore, people are unhappy with everything because they know game to well. So the solution is to resurrect what they once loved (when they were newbie and new at l2).. meaning the old servers, that way it will last more and they get a piece of what they once loved.