You see it all the time on private servers, boasting about the nostalgia factor in having old school servers.
Even runescape did it.
I think A LOT of people would come back to playing maplestory if Nexon released an older server like v62 or v83
They should focus on party quests being a HUGE role in the game again. And keep it so we only have a few job classes and skills that can't wipe entire maps.
I've seen this work successfully on a specific private server and I'd love to see it on a large scale with Nexon backing it.
And for funsies, add an option to make hardcore characters (If you die they get deleted)