If you could do 5 things...

[fixitman]

1> Fee-based one-time name change
2> Vote-kick for instances
3> Increase leve allowances gained per day, based on level
4> Every time a character uses "gils", "$", and "safe" in yell or say, more than three times in a 10 second period... their computer explodes
5> Free cookies!

[Livilda]

1. Sell Fantasia.
1. Votekick.
1. Chat window blacklist/report.
1. Server name included in cross-server DF parties for easy blacklist and report.
1. Deadly tornadoes at every real-world RMT office location or home.

[jcw005]

1. More cowbell.

[Fenrisen]

#1: Introduce a card game similar to FF9 where you can duel other players. Make cards rare drops from monsters. This will keep players entertained.
#2: Spectral chocobos like in FF7. I want me a black chocobo.
#3: Mount racing! Make them able to be customized via stats, like endurance, overall speed, speed boosts etc etc. to provide an added challenge.
#4: Make Foulques a more prominent character. He's cool.
#5: Use of the up arrow in chat to recall the last character you /tell'd.

[Pendragon72]

1. Get rid of gold sellers(RMT)spammers
2. Get rid of gold sellers(RMT)spammers
3. Get rid of gold sellers(RMT)spammers
4 Get rid of gold sellers(RMT)spammers
5. GET RID OF GOLD SELLERS(RMT)SPAMMERS

[Steeled]

0.) Right click blacklist, sorry this is so easy, it doesn't deserve a spot.
1.) Party size increased to 5. I play tanks and healers, but 2 dps expects too high of a tanking and healing population that's never been represented in any mmo I've ever played.
2.) Buff exp from leveling dungeons, buff rewards from capped dungeons
3.) Add more dungeons.
4.) Make Leves more rewarding.
5.) Take abilities off the GCD that shouldn't be on it and simultaneously get rid of the animation lock.

[Khalette]

4.) Make Leves more rewarding.
5.) Take abilities off the GCD that shouldn't be on it and simultaneously get rid of the animation lock.

Good ones.

[Cyrus-Wallace]

1- Make dungeon monsters to drop chests with low chances but randomnly with some loot according to both the instance/level.
2- Kick function.
3- If there's Zodiark, why not Belias, Mateus, Fámfrit and the others? I want them ingame!
4- Gunblades. Seriously.
5- Minigames: Triple Triad or Bliztball.
6- Monster playable races: Bangaas or No Mou as previously mentioned.

[Makomin]

1. Add ninjas
2. Fix the targeting system
3. Fix whatever is causing melee to have difficulties with hitting moving targets
4. More variety in high level activities worth doing (not just CM for philo and AK for myth). Could come from improved rewards in existing dungeons like wanderer's palace or through new dungeons.
5. Random loot everywhere from monsters. This one is unrealistic for this game, but I love a huge variety of loot and the chance of striking an amazing item from a random mob Diablo style. Maybe, at least, rare unique item drops from random mobs.

[samst]

Vote kick.
Being able to get new players in Primal fights in case someone leaves (Why do 7 people have to suffer because of 1 rage quitter?)
DoH's to get a "Set-up-shop"-toggle, making them become a "NPC" that melds for a fee of their choice!
Fat-monster grinding in groups to be extremely viable. AFAIK FFXI had this, so did my first love, Dark Age of Camelot.
More hair styles and a barbershop!