I've addressed this in an earlier post, but FFXIV is a good fit for a "toggle option" because it doesn't have actual player factions that hate each other. PvP is presented as friendly competitions between the grand companies (at least in the Frontlines). But outside of PvP, an Adder player can walk into Maelstrom HQ with no fear of being toggled involuntarily to PvP.
So the only players who should be in the mode would be those who do want to PvP.
