Recycling the other faction zones is not a popular decision, and it has turned away a lot of people from the Veteran Zones. Players who enjoyed immersing themselves in the game have reported their discontent of playing these "alternative realities" because it ruins a sense of faction loyalty.
Sabotage and assassination alternatives in these quest lines have been suggested multiple times. I whole-heatedly support this idea and would make the Veteran Zones much more enjoyable.
I play in the Aldmeri Dominion and miss working along side Razum'Dar and the Queen. (Not to mention that Queen Ayrenn is much more competent than the High King or Skould-King; you don't have to save Queen Ayrenn repeatedly.) After you complete the quests in your faction, you really don't see the influential figures in your faction anymore because they get frozen at the last quests you've done.
My suggestion would be for these characters to give dailies for End-Game PVE content in the Veteran Zones. These Dailies can be sabotage, assassination or gain the trust of X figure quests. These quests would promote faction loyalty immersion, give TRUE end-game content and keep us playing with figures that we've enjoyed playing along side during our faction's quests.
This would open up great possibilities for new reward systems. Faction Gear can be a reward for finishing a rare Daily or even a new set for Eye of the Queen gear like Razum'Dar wears (and equivalents for the other factions).
Razum'Dar is a capable spy that could infiltrate enemy cities to give us these dailies. The other factions also have capable spies to infiltrate their opposing factions.