So it would be on a brand new server then? Putting it on an existing server would simply destroy the community there. Also; since we all essentially play on a single faction, how would that be reconciled with the main scenario/lore? I mean the whole Gc vs GC thing is already forced and ill fitting. Will we suddenly have access to a Garlean faction? FC vs FC? Why? (though there are certain FCs I wouldn't mind camping in their front yards). You can't simply shoehorn this in. As with everything else FF, there has to be a valid in-game reason for it.
EDIT: that line in Star Wars "you will never find a more wretched hive of scum and villainy" describes PvP servers perfectly. In every game they are the worst of the worst. They attract bottom feeding scum like nothing else in this world. They make Revenants Toll trolls look like reasonable people. Why would we want this?