One of the things I enjoyed about other MMOs is certain areas having world PVP. It added interesting dynamics to the game, enabling new kinds of friendships to be made as players banded together to drive back other players, or defend towns and such.
I also really enjoyed the guild vs guild PVP in games like Ragnarok Online. For many years it was the only reason I played.
I think the developers are missing a huge opportunity by not having certain zones where players can either capture or erect castles which need to be defended during specific PVP times against other players.
This is what I'd like to see:
A new zone (maybe Al Mhigo) opens up where Free Companies allied with Eorzea kingdoms must capture land from the Garlean Empire, taking their forts and castles. Some areas will require owning an airship in order to invade and perform aerial bombardment of defenses, and only by using other airships can players take down a FC's airship that is bombarding their castle.
Basically, airship combat would work by having some players manning cannons, while one player controls the ship. The objective is to do enough damage to one airship to make it unable to move, at which point that airship can be invaded by other airships crews who fire grappling hooks to strap the two airships together. If the invading crew reaches the control room of the airship and destroys the engines, the airship explodes (everyone inside the airship parachutes to the ground below).
For game mechanic reasons, destroyed airships can be easily repaired by spending like 100k gil or something.
However, new Free Companions can be created that are allied with the Garlean Empire, to defend these castles or recapture them from Eorzea allied Free Companies.
A Free Company can capture a fort by fighting their way through the rooms to destroy the Aethernet crystal in the final room. After destroying the crystal, the previous FC that owned it can no longer teleport back inside, and a new Aethernet crystal is constructed with all members of the capturing FC now attuned to that crystal (this is similar to the War of the Emperium event in Ragnarok Online).
FC who control a castle can spend gil to buy defenses for that fort, such as cannons or even trained monsters (imagine setting up a wave of Marlboros to defend your fort's moat, or having a bunch of hired beastmen defending the crystal room?). Owning a fort allows special perks, perhaps access to special furniture items for guild housing and other bonus abilities specific to PVP.
You can also add 'Alliances' to the Free Company system, enabling several Free Companies to be allied together and able to share a captured fort.
The forts could only be captured during specific times of the day and week, with a 1 week waiting period between PVP battles. This would ideally be on a Saturday, probably in the afternoon.
I think this system makes a lot of sense in lore, as Free Companies are supposed to be reserve military units for each city, but we currently don't really do anything as a free company to participate in military affairs.