I don't like the idea of a 'separate' factions world in any form.
It's apparent that my opinion is unpopular but I will explain my reasoning either way. Before I start, I participated in the PvP/Factions discussion on the MassiveTS a few weeks ago and know about the topics discussed.
Reason #1
It won't be successful... Yes, It just won't work out in the end. The current factions player-base has littleraly invested years into the current worlds, I doubt anyone is willing to ditch that much time, effort, and memories.
Reason #2
If the new world is successful... It would divide the factions community. With the factions worlds struggling the way they are- pulling away players is the LAST thing we want to do. New players would be divided on the decision to play on the 'new' world(s) or the 'old' worlds. If everyone starts to switch over to the new world(s), what will entice the new players to visit the old worlds, or the old players to stay in the old worlds if everyone is in the new world(s)?
(I've changed my mind, I won't be adding on to this comment.)