I think it was the last time in 2013 when RPG club was really amazing. And it was the first time in hell knows how many years and different servers when me and my friends kept playing for almost a year and even the overall online stayed very high for more than half a year. Since then no servers have reached such high potential and success... So the question arises - why it was so successful?
In my opinion, it is because it was just like every official RPG server in every MMO... It was being constantly upgraded. It was DYNAMIC and always changing. I do not remember the details, but lets say imagine that...
The server starts in the Kamael chronicle, everybody can create their favorite characters, but low rate there is not such a piece of cake, its relatively hard to farm and it takes time to get that sweet s grade. Kamaels may be a bit too powerful but not too much to be very annoying. After a month or so you hear the news about hellbound update, everybody is excited, finally we get a new huge playground (which I think did not even open before I quite rpgc last time as it was quite irrelevant in h5). In pvp - some classes get stronger some get weaker, market dynamics change and everybody wants to get that sweet dynasty gear, foundation items also become available for those who grind extra, and another great thing is that S grade you farmed before is still not absolutely useless and it becomes available for more "noob" players that are not in top clans/CPs, as long as you manage to put on some attributes on your weapon! After a month you hear the news that everybody should get ready for Gracia! And maybe lets add some events together with the update. Again, current players get excited and some people that previously left the server get a reason to come back. Gameplay dynamics change, market changes as CPs and top clans start selling more valuable items in giran, olympiad dynamics change again, some chars get stronger some weaker. And again after some time we get the H5, s grade becomes just an accessory or a thing to enchant but we already enjoyed it for enough time. Everybody wants that sweet vesper and those sweet new skills, and thus the grind continues... Time to kill some ugly tumors!
All in all, this is just random details how it could be, I am sure that experienced server admins would know much better when to implement these updates and which versions to skip, which to choose. Or even make a vote each month. But the question is, what you think about the idea itself?
P. S. It was x15! I think it would work even better in x7.