The funny thing is... all Open PVP MMO ends to fail because of the flaw this systen has : you can't mix PVE quests and PVP. You have to make a choice PVP or PVE but don't mix them. They solve it with... "PVP servers" in order to survive and... most of time you see many more PVE servers than PVP ones. Or they add opt-in... and most players chose to remain out.
There's nothing worst than PK when people are doing the MSQ. People just leave the game. It will not make "empty" old maps more populated. It will only lead people to go away from the game.
SE made the right choice for FFXIV.