Concepts from other MMOs that would be utterly anathema to FFXIV

[StriderShinryu]

I play alts in FFXIV but GODS this game is the most alt unfriendly I have ever played and it's incredibly frustrating....
No mailing between alts. No shared retainer. No shared housing. No shared mounts/ minions (although that is not as important to me I know many people who are frustrated because they have to buy/ farm their favourite mount/ minion again and again...). Only very few account-wide mog station items.

Yeah, I have to agree with this. I love how completely unnecessary alts are in 14; it really is one of the best elements of the game. But, for when you do want to try out an alt for whatever your personal reasoning is, it would be great if FF14 wasn't so terrible about it. Even something as minor as a shared retainer would be a godsend.

[Barraind]

Horizontal loot progression.

Non-cosmetic character customization / progression.

Ability to jump into endgame content within a week or two.

Built-in add-ons for skill/performance improvement.

log-out to character select to avoid a log-in queue if changing characters.