I would like jumping. Jumping allows you to develop future quests and dungeons with unique action-oriented mechanisms in mind.
One of the best pro arguments so far.
3-dimensionality really expands what you can add to the game.
I also chuckle whenever I see some stupid WoW Goblin hop around
a pole for half an hour, but who says this would be possible in FFXIV?

Just make "Jump" another stamina-dependent move, et voila: problem
solved. And while you are at it, also add "sprint" as a stamina dependent
move.

Just imagine how this would expand the demands on player skill: Jump to
evade Vrtras tail sweep, and sprint to escape those 1000 needles. Stupid
bot forgot to jump? Well, sorry Mr. Gilseller...