General Suggestions

[KinZoku]

Give an option to limit the number (or remove entirely) character models on the screen, excluding Party members, when doing events such as F.A.T.E.'s.
When you're doing higher level F.A.T.E.'s, then it's typically very crowded - this means that on the occasions where Bosses/NM's spawn, you very rarely actually get to target them because they seem to have a lower priority than NPC's (Chocobo/Pets) and Players. On some occasions, I can target them and then they vanish again.

Remove the inability to use a mount when you're fighting with your Chocobo.
I have 4 mounts: Legacy Chocobo, Company Chocobo, Coeurl and Goobbue - Why can I not ride my Goobbue or Coeurl when I'm fighting with my Chocobo? My Chocobo can keep up (all mounts run at the same speed), why do I have to burn through Gysahl Greens if I want to use them?

[KinZoku]

Alter the way targetting works.
The filter system is great, but on PC/Keyboard&Mouse it doesn't seem to do anything - that could just be me being incapable of doing something though. Make use of the Filters and a single targetting key - if I have "Enemies" selected, then I can only cycle through Monsters. If I have Friends, then I can cycle through players (I have no idea what the use of "Party" is, but no doubt it's useful for Gamepad players). "Others" should allow me to cycle through NPC's/White targets (such as Aetherytes) and "All" should let me go through absolutely everything. By default, F1-F8 covers party members on keyboard - these should be left alone and regardless of your targetting method, you should be able to target them (for example, if my filter is on "Enemies" and I hit F3, I should be targetting the third person in my party). On Final Fantasy XI, almost every button was multifunctional.

[KinZoku]

Allow the Pet hotbar to be removed/hidden on PC.
Most people are likely to have actions they want their pet to do, assigned to their standard hotbar, so those bars can be used by multiple classes without fiddling with Keybinds every time they change and so they don't have to use the mouse in the middle of a fight. I've heard it's possible to hide it on the PS3, but I've never played (or seen) it outside the PC.

[KinZoku]

Increase base EXP yield.
Let me preface this by saying: I haven't done any EXP PT's yet. I've been working on the story missions with a friend of mine, and we're generally taking our time (enjoying the scenery, etc).

I have, however, killed regular monsters before (non-FATE enemies) for around 250 exp/kill (around 2 levels higher than me, with +50% bonus), for Chain 4 I was looking around 500. I believe increasing the base EXP yield to around 400 would make it plausible to EXP outside main story quests or FATE's.

[KinZoku]

However, with the speed the game is going, I don't think 250/kill would be suitable when you need almost 500,000 to get from 49-50. Assuming a slow EXP PT, killing 1 monster every 30 seconds, it would take approximately 16.5 hours to get that one level. Assuming they kill a monster every 15 seconds (which is more likely, equipment depending, player capability depending, etc) then you're still looking at 8-9 hours, which is a lot of grinding out EXP for a single level - especially when XIV was originally aimed at the more "casual" crowd for things like levelling. While I don't think 8-9 hours is so outrageous I wouldn't play (though I think 3-5 would be much better), I think it would be nice to have the option for reasonable EXP from a mediocre party, opposed to simply FATE hunting for the third, fourth, fifth, sixth, seventh or eighth time in a row. Dungeons can provide a reasonable amount of EXP, but doing everything in low level dungeons negates the point of gaining new abilities.