First off all, if you want to use the world oldschool, its gotta stay oldschool.
Also to attract the most playerbase you gotta get rid of the p2w shit.
I made a list for you:
-Decide the cap, keep it CHN Only ( 80cap / 100cap are the ones which most of people like.)
-Keep the map small ( Jangan, Dowhang , Hotan Area only), Players like to see other people arround them.
-Add at least one Fortress War, doesnt matter how oldschool it is (dont forget fw is the one of the things players enjoy most)
-Server Capacity and Limits (Keep it max. 3500 Players and set your HWID limit to 1, this will help the server with a real economy and longer lifetime.)
-Allow bots, but do not allow afk botting.(Protector mobs, and a punishment system should help with that.)
-About silk items
+Remove everything that gives you an advantage - dmg scrolls and else.
+Make silk items non-tradeable so it will be character-bound.
+add 1 standart full dress set,premium and devil to a shop for premium coins (also non-tradeable, this should kept away from the game/gold economy, otherwise it will fail after a point), this way a non-donater supporter will have the same chances.
+item mall alchemy stones: should be added to all uniques as drops, this makes uniques great again, nothing to pay here, and another element in the economy.
-jobbing: tri-job system is the way to go, keep it original.
-rates: Keep it 1x, work on the silkroad quest system, push people to make quests to get high levels, make them do shit instead of grinding hours. Keep the game simple as it was, but make it more appealing.
-last tier items:sos, som, sun should be special.
+Take an example : 100cap chn only, last tier items 98-100lv, last tier sox: 90-92, all of them are good, people will grind for 98-100 make them +7or more and play with them, because it is worth it. ofc till they get their hands on sox items, this is the only problem we have, how should people get those items? lets think about that. Nobody should have to grind endless hours to get them! add them as special quests rewards, which only can be done after playing a good amount of time, look to other mmorpg games like ffxiv etc., how are they doing it.Quest example
Kill All Uniques 10 times each!) add them as special drops with a very low rate? add them also as normal drops at a very very low rate? Dungeons are also a good way, forgotten world is a good system, you spend time, also with luck and hard work you can get good items, keeping fgw can be good , but it should be more fun! this can be discussed- but you gotta keep it simple, adding too many coins makes just the economy worse and people get boring.
I myself plan on a server in the future similar to this, i am waiting just for the right point with the servers on the field right now, but i am happy to contribute if you look for people.