The autoattack alone would make them redesign the battle system from nearly scratch.

The Dmg equation has to be changed (if they are doing anything like XI's system), tp forumla has to be changed, they have to remove the stamina bar so something else has to limit things so rebalancing of all the traits and abilities. the weapons have to all be changed with delays and what not, animation might have to be altered to make it not look awkward.

I see that 1 simple change probally being a mountainous amount of work.

Simple making your character attack nonstop would not work at all with the current structure of the battle system.