Since we have destroyed the masters of the planes of life and water now, at least according the the lore in game, why not allow us to use those planes to launch PVP invasions on our enemy factions. Much like the current pvp rifts, allow it to spawn a base of sorts, launching NPC raiding parties to go hit key enemy locations in a zone and allowing the group who launched the invasion to port directly to the site of the invasion to go on the offensive.

Rewards could pretty much be similar to what is given now, and perhaps throw in a NPC Hero that is summoned after certain objectives are completed by the defense to end the event, making it work much like current invasions, only with player involvement being more in direct opposition of each faction.