If Square-Enix directly asked you for suggestions...

[Erudito]

Combat jobs: Give a job a theme and stick with it. We already have cross-role, so go nuts with the job stuff.
Black Mage: This jobs method of play (low movement turret) is completely counter to how you want us to handle mechanics. In future expansions, I would request a way to cast whilst moving.

Glamours: This game has shared gear with job types, give us a way to give the same gear multiple glamours and a way to save said glamours because its an issue of space and it restricts our creativity.

Treasure map loot: Currently, stuff that exclusively belongs to treasure maps, Uznair and Aquapolis are either insultingly expensive in the market or non-existent. Please do something about this. In my server there are no music sheets that drop from those places and the materials for the new glamour are over the 10 million gil mark and no actual glamour item for sale. I consider this to be insulting to us all and will be making an official request to have this mended some other time.

[Mimilu]

-Differentiate the gameplay between jobs more, especially the Healers and Tanks.
-Add more end game PvE content. Right now we're stuck with Weekly grinds and/or Savage Raiding, with the occasional EX primal (which generally don't last very long). There should be a variety of things to do, where people can pick and choose what they want to focus on.
-Think less linear in all aspects of the game, please. You need to think more horizontally if you want anything in this game to have some semblance of longevity.
-Ask SE for more money and staff so you can do more and better things. :B
-Give FCs more things they can do together.
-An Over-Head view would be nice.
-Maybe stop raising the level cap every expansion. Maybe do it only every other one instead.

[Elkanah]

Black Mage: This jobs method of play (low movement turret) is completely counter to how you want us to handle mechanics. In future expansions, I would request a way to cast whilst moving.

Answer:
https://imgur.com/a/UzPSM

If you know the boss, the mechanics, and the mobs you face, you shouldn't even need to worry about it as much. You're a competent player I assume, so if you know how the mechanics work and know when or how to dodge the content as is right now, you should already have this or know when to adapt to the situation. As a BLM And RDM myself in savage content, this is nothing new. BLM has always been like this since 1.0. They've actually made our job easier with the triplecast ability and an ohshiii button in situations like these. Hence why we have it. You may just need to consider reading into the mechanics more and knowing the fights and play much better if it's too much trouble is all.

[Airget]

Simple one, 24man raid gear should have a similar upgrade tier that you pay Creation Tomestones to upgrade. This would open up more variety in terms of BiS

[Aldora]

Tail armour.

Funny enough, the Darklight tanking set had that in 1.2x:


(Left picture is 1.2x and right picture is 2.x)

[DarkDedede]

Alt friendly features, such as easy inventory transfer and storage sharing.

[Anienai]

What would you tell them?

1. Purge Lalafells from the game.
2. Beastmaster class
3. Better class story
4. Remove or lower debuffs from each class and then create a debuff tank class.
5. MCH with dual guns or bazookas.
6. Redo DRK battle animations.


That's all atm.

[DNO]

Merit points.
Everytime we do a dungeon or weekly tomes or weekly raids or savage lets get an extra bonus.
Let’s use these points to customize our characters. Like 10 merit points increases ruin damage by 1% for smn. Or another smn uses it to increase bio damage etc.

[Science66]

Small request: "recommended gear for retainer" button. Gearing my retainers take way too long, maybe I'm doing it wrong XD

Genie emerges from lamp and asks me for one FFXIV wish: Alts can skip MSQ if your main has completed story to max level.

[Ayer2015]

Change item level progression from every 6 months to every 3. Odd numbered patches feel like content droughts.