Hmm. I like the cut of your jib, sir. If you DO fire up a server, color me interested-- details notwithstanding.
I've been on-and-off with RO like a bad girlfriend for the better part of seven or so years now, and I have a fairly good understanding of many things about it. From what I've seen, here are my external observations:
1) There is an absolute pressing need for a multi-lingual support of some kind. Many of RO's players are from non-English speaking places which makes it very important to not only welcome them if you're gunning for a server with double or triple-digit population, but to continue to make them feel welcomed and involved. It'll be tricky since a lot of servers lean the other way-- just welcome them, which is fine, but English players like me often enter the server, feel immensely estranged right away, and typically end up leaving which usually stagnates the population pretty heavily at a certain number (usually the low- to mid-100's).
2) PVP is not WoE. They are different entities entirely and a PVP-based server is usually the one full of jerks and trolls, while a WoE-based server-- while not without its share of troublemakers-- is going to be full of players more willing to spare details and the time of day. Encourage competition in some way, shape or form so that one guild does not end up owning the server.
3) AVOID DONATION ITEMS. SERIOUSLY. If you aren't prepared to maintain a server, don't do it, it's not worth it. As soon as you add incentive for players to play that is extraneous like donation items, you end up with this massive rift between players and the whole idea of a game that's... er, 'free' (I guess? poor Gravity) because horribly unappealing as you're basically one of those many butchered F2P games where people unwilling to shell out their cash just get the shortest end of the stick possible and usually end up experiencing a stunted game for it. Of course, your donation items could be acquirable in-game too, or could just be purely fashion-related-- I like the latter because it gives some recognition and a neat little plus, if you absolutely need to reward donations. Headgears with the same stats as stuff already acquirable in-game, but with various aesthetic appeals could be a route.
4) Just disable GTB. Nobody likes that card anyway.
You seem like you've got a reasonable head on your shoulders-- but be prepared, because most RO players don't, so you'll be in for a hard and rocky ride through the annals of RO server-owning.
You should shoot me a message when you've got a verdict on what you're gonna do, eh? I'd be interested to see what you've got going, when it gets going.
As for what I expect, personally... as long as the GMs listen and the community isn't a giant pile of elitist jack-offs, I'll play it; I prefer mid-rate and up (because spending two hours grinding from Novice to 1st class is not fun no matter how you swing it) but it seems to me low rates always get the best communities. I also love a server that has frequent enough WoE that is polished, paid attention to and well-cared for while being competitive all the same. Also, I hate plethoras of customs. RO has an ungodly amount of items as-is... while some endgame quest items are great rewards to work towards, we don't need like seventeen NPCs each with twenty items to make that require oodles of materials that basically just require unchallenging hours of grinding at porings or something. If you're gonna make custom quests, make 'em as follows: Group-oriented, challenging bursts that require 3-6 ingredients either in singles or modest amounts that can be acquired with a little prep time and a well-formed, well-informed group-- or find some other way to optimize it, but for the love of god don't make me grind for six hours to get purple boxes to click-click-click to pray I wind up with the 40 dyestuffs I need. No. No. No.
Low rates encourage strong teamwork and community because generally, each class-role needs to be filled even in the most elementary of parties. High rates aren't this way because any one character can level easy by picking on weaker monsters and thus circumventing the need for a party; mid-rates can fall on comfortable middle line where partying has distinct advantages but is not necessary for most or all classes... though sometimes the community still adopts that individualistically elitist notion that they don't need parties, teamwork or anything that doesn't directly benefit them. SHR server communities don't exist; there's just a bunch of asshats in the PVP area(s) teabagging corpses capslocking obscenities. Fun? ...right, anyway. Stick to Mid- or Low-rate to see the best kinds of communities unfold. A natural, latent encouragement of teamwork in the community will build it strong and build players who are both willing and ready to help and tend to discourage acting standoffish.
...whoo! That was a wall of text. Anycase, hope any of that is useful or something.