A lot of great replies and great ideas for revamping zones thank you everyone.
To answer my own questions the primary reason for revamping old zones in terms of story relevance in my opinion is that Cata developed the zones to be tied to Cata’s story. Most of those zones have had significant story developments since then and would benefit from being updated/revamped. Also, they would be more fun to play through if they had their own stories rather than being tied to one expansion.
While in my opinion a world revamp would be preferable there are some story reasons not to do a world revamp. The simplest being that the stories of these zones are well liked by some and they would be sad to see them removed. Another is that many of these zones are tied to the leveling process. That being said the current leveling paths available to players are confusing already so there may not be much reason to keep them.
As for what zone I would like to revamp most (cracks knuckles) I would want to revamp Westfall. In particular there are four major changes I would make to the zone and its story. For one thing I would have the drought that has been ravaging the land finally end and for settlers to start to flood into the zone. The story would open with a dispute over land between settlers that would need to be resolved (players being key to helping with this). From there players would learn that two noble families are attempting to manipulate the situation to their advantage by either helping the settlers or sabotaging their efforts.
The zones main story would focus on how one of the families is going too far by using the memory of defias brotherhood to intimidate the locals and settlers alike. In particular they are using someone they claim to be Edwin Van Clief’s true heir to rally support and scare people into submission. Vanessa Van Clief arrives in the zone and is able to discover that this person is the daughter of the Fullbrow family and that she is only cooperating with the nobles to protect what is left of her family. Vanessa works with players to rescue this girl and her family and to show these nobles for what they are. The effort is successful and the nobles flee to the Deadmines to make a last stand.
The story concludes with Sentinel Hill finally completed and the effort to heal the land well under way.