The zones could also be scallable so that high level players are scaled to a lower level if they are in a lower level zone. This will make PvP balanced and low level players will not be killed by higher level ones. The only issue with this is even though higher level players will be scaled to a lower level they will still most likely have more spells than the lower levels since their actual level is higher. That doesn't mean that the lower levels won't have a win condition, but they will just need to use the terrain and any advantage they can think of to outplay the scaled higher level.
~ Yours Truly
I think this will be very difficult or even impossible to do. Certain weapons, spells etc will require specific lvl, stats etc. If higher lvl player goes to a lower lvl zone, you should lower his lvl and stats which will result in "losing" some of his weapons/armors/spells/stats. This will make the game more difficult for the developers and for the game engine.