C1 with low rates(x1-x2), best equipment B grade and max lvl 70 or 75...people want hardcore and have that nostalgic feeling for such a server imo.
A server that they could dedicate some time and the fast lvling isn't the first priority.A server that makes the game hard and rewarding.
Like the achievment that Korean and Russian L2classic servers had with hardcore hybrid C1-C2 servers (you can take a sneaky peak at youtube streaming vids) and now they are ready to open for Europe too the same after they got over 16000 votes for it.
It would be nice if you consider making a hardcore c1 server