Nexon should add a legacy server that would take place in the "pre Big Bang" era, where 200 was the cap, you had to have a team alongside you to fight hard bosses and party quests, such as cwkpq, zakum and when the spouse PQ in amoria was still useful.
The game was so much more balanced than it is now and it was just a really good state even with it's super grindy leveling system, it felt really rewarding.
It worked with World of Warcraft, RuneScape, and i am sure it would work with MapleStory. Literally everyone i know, including people i met on the game says they didn't like what was done after Big Bang, myself included.
I believe it would bring a LOT of people back to the game, again, myself included.