What I think would be a nifty tool in Maple would be a character storage system
What I think would be a nifty tool in Maple would be a character storage system that holds characters when you do not have enough visual slots. The character storage system would allow storage of up to 100 universal characters (shared with all worlds except Reboot, which will have it's own storage of up to 30 characters), that can be switched out with currently placed characters. The Character "Cloud" as I'd call it, can also be used to store characters with deletion in process statuses and allow us to instantly create a new playable character without having to wait 24 hours because of the security reason.
Character Cloud Functions:
-Can be used to transfer characters across worlds (except to Reboot and Scania.). Characters in the storage can be transferred to any other world once per scheduled maintenance. Only one character can be transferred per maintenance. Characters in Scania can transfer to other worlds but can not you can not transfer characters to Scania unless your character was originally created in Scania.
-Can be used as means to bypass 24 hour character deletion to make new characters (characters awaiting deletion still have to wait the 24 hours, but will be in the storage rather than taking up character slots). This removes a lot of the fuss with people having to wait to make a new character if they used up their current slots.
-Can be used as an external storage to store items and up to 500m maplestory mesos. Characters with over 500m mesos must place excess ms2 mesos in the storage in the game within their world. (This is to prevent people from heavily abusing world transfer as means to abuse other worlds' economies. You will be abled to bring items over between worlds however to prevent a significant rise of meso transfers, the transfer limit is capped, and as noted above, the world transfer limit is only for 1 character per scheduled maintenance.)
This is a rough sketch of what the storage would sorta look like:
I'm not sure if this would be something players would want in the game but it's something I think should be available to everyone.

May
Make the Job Change Tokens from the Gachapon tradable to anyone
Then there's "that guy" who sees the high levels that are paying 1b to job change and go "They're paying 1b, so let's make the price of these job coins exactly 999,999,999 maplestory mesos!

Mar
Shadower adding a "Shadow Stretch Skill"
How it works is simple: You can only bind 1 enemy (including bosses), and if it successfully touches an enemy, it can splash chain to other enemies at half the original attack range, binding up to 7 more enemies

Jun
Maplestory Miracle Cubes and Potential need massive changes
Now some people may argue that you can craft these cubes, but the reality is that the people who craft them are generally high level and high funded players anyways.

Feb
MapleStory Hero skills suggestions
Now, my own suggestions. On end game, since Panic only does 1 line and doing 1150%, looks close to 4000% if i count combo attack, enrage and chance attack, I really think it is time to raise cap damage on Panic, like Marksman Snipe, so at least 400M MapleStory Mesos.

Jun
Suggestion - Party Quests Revamp
Now we face here another problem, if all of the PQs will be revamped so people will start one PQ then will move already to another PQ because leveling is easy today.

Jan
Maplestory Familiars Remastered
This is my idea summed up (the minor details are not to important). I feel like this, or something along these lines will really make familiars a more interactive and useful addition to the Maplestory