RO in 2014
Dead. I doubt there are ACTUALLY new players will play RO due to what above poster said, RO can't cater current generation's demands. Almost no quest, involves crazy farming to gear decently, and there's nothing exciting on doing stuffs that can be done by bots. Only people who you can invite are the RO veterans themselves.
No, adding headgears or stuffs won't help. In RO, ONLY your head sprites changes when you put different gears. In current MMOs, you can dress up EVERY part of your body and be stylish. The only thing RO can do is to use Stylist.
What will interest people
Grinding : hell no are you serious.
PvP : maybe, RO is kinda good because you don't really depend on gears like today's typical MMO where gears BEATS skill. but then again, if you don't have "ignore DEF" skills (like GFist, Acid Demo, etc) I don't think the first sentence applies.
WoE : FE, no, I don't think people like to run around maze-like castle while getting smacked from high ground. SE, maybe. So far WoE is the best GvG system for me. Only downfall is that it's spammy as hell, so you either use AHK and other kits, or you're going to break everything.
Headgear : if they're fans of 2D, kawaii graphics, maybe, but then again, Maplestory exists, also there are cute 3D MMOs like Spirit Tales/Eden Eternal.
Custom contents : I haven't seen any custom contents in RO that actually beats today's current MMO though. Questlines, etc, today's games won, so yea.
How to introduce new players
"Wanna play a cute, 2D games that is NOT Maplestory?"