The reason it works in something like WoW is because it was part of the game from the beginning, and it works into the faction conflict story.

Not only does FFXIV not have any of the framework required for something like this (for example, characters that stay in the world during cutscenes are effectively invincible, and teleport around a lot), but it wouldn't make any sense for adventurers to beat the snot out of each other in front of Hraesvelgr.

...it would be fun, though