In the 20th anniversary video for Maple Story, Classic World was announced to be in the making along with one of Wizet's head developers leading the charge.
First and foremost as a Maple Story player since Version 0.24 I want to say thank you for bringing this out for all of the player base to experience and enjoy.

That being said, I want to take advantage of Nexon's and Global Maple Story's promise to review and acknowledge player feedback.
I think it goes without saying but I will say it anyways, there is no surefire way to satisfy a player base entirely. There will always be a divide amongst players on the content that is desired, and often times we have seen throughout the years that the player base is unsatisfied with the very content that a majority pushed for.

With this is in mind I would like to make my first suggestion a vague one; (1) Feedback isn't always the best way to improve content, so limiting the impact of player feedback into the vision for Classic World might be more beneficial for the longevity of the server.

Many Mapler's don't truly know what they want. We've seen this happen with many updates and patches in the original game, to a point where the identity of Maple Story has deviated from Wizet's vision for Maple Story entirely. I do not believe that monetization alone is what impacted Maple Story is such a negative way but rather the changing of the game's identity entirely is what lead to many players becoming less interested.

My second suggestion would be on the topic of monetization. I want to say in advance that I completely understand that this is a business and the intention is to be successful in order to justify the investments for development.
With that in mind, I do believe that Classic World, if done correctly, can single-handedly generate more revenue for Nexon than the current original Maple Story.
I believe this because I played the original game, and I alone spent thousands. Many players did.
However, some of the content of the original game did help lead to the destruction of the server. It was unhealthy for the Game's in-game economy and 'Free Market'.

(2) I suggest to lean more into cosmetics, 2x exp/drop coupons, shops, pets & pet equipment, megaphones, hairstyles and beauty parlor coupons, etc. and LESS into items like the Gachapon tickets.
The gachapon and itcg items were an amazing addition to the game, but it locked a lot of powerful and useful items behind real money, which gave many players an unfair advantage. People with a lot of purchasing power had more opportunity to hold the game's Free Market, ultimately disrupting the capability to "Play to win".

My third suggestion is more of a personal preference, but I believe many lovers of the Classic Maple Story experience would agree with me.
(3) Stay true to Wizet's vision for Maple Story, and not Nexon's.
The fourth job advancement in Maple Story was the real beginning of the downfall of Maple Story. Many players will disagree, but it's the truth. The identity of Maple Story changed with Fourth Job. The justification for my claim is that the Magician class alone was a primary factor; Blizzard, Genesis, Meteor Shower made "Leeching" the most viable option for leveling. This is seen throughout Private Servers who illegally pirate the game, but it is a prime example of how the game isn't leaning into a Classic experience.

The classic experience is to spend the time, the hours of grinding for levels, to have skills that make each of the FOUR class titles viable in their own, unique way.

I watched the video that was showing some of the current gameplay of Classic World in the 20th anniversary announcement, and took note of some of the potential changes.
There's a new 'Guard' feature, which looks to adjust the 'Miss' function when a monster attacks the player. (4) This seems like an interesting adjustment, and I do think that some of the original values of things such as Weapon and Magic Defense for players should be adjusted because they weren't very good in the original game.

The swing/punch function of ranged classes seems to be removed, ultimately allowing ranged classes to stand and shoot or throw stars without having to create distance or "Kite" a monster. (5) This gives me a lot of mixed feelings because it's not Classic, and also removes the need for skills and functions like "Knock-back" and "Power Knock-back" as well as removes the need for Flash Jump being a justified skill to create distance from a monster rather than being a glorified movement skill. Not to mention Shadow Web being completely useless if there's no need to kite.

At the end of the day, I personally believe that Classic World really should be nearly identical to the original game, with minor adjustments and mostly graphical and UI overhauls.
The content progression should end at third job, and from there I believe that the content to be released from that point on should be true to the Wizet style of the game; slower pace, and linear to Wizet's style of bossing. (6) If there is to be a fourth job advancement, I highly suggest that this development team takes a completely new route, from the names of the classes to the skills and the content to obtain the job advancement being completely changed and redone. Please do not add in skills that can wipe out of a map's spawn. This is never a good addition to the game.

Thank you for listening to my feedback and I hope that my suggestions reach those who read it.