We all know that world PVP at present will not be allowed.
From what I have witnessed here in these "unofficial" forums, there is a large number of users that support the idea of world PVP.
I admit that I do not know a great deal about this game's design or about game design in general, but I have extensively played through 8 major MMO's over the last 10 years.
Here is how I would do it:
1) Allow me to "Flag" myself for PVP, and then:
a. I will be instantly teleported from my factions instance to the "PVP" instance.
b. Once I enter the PVP instance there is a 5 minute cooldown before I can return to my faction's instance.
c. After leaving PVP combat, there is a 5 minute cooldown before I can return to my faction's instance.
2) Instance zone chat from the PVP instance.
a. This will prevent players that are flagged in the PVP instance from requesting aid or forming raiding parties to enter the PVP instance from their faction's instance.
b. When someone receives a tell or whisper from someone that is in the PVP instance they will receive a 2 minute cooldown before they can enter the PVP instance.
3) While entering a major city from the PVP instnace you will be immediately teleported back to your factions instance and will receive a 5 minute cooldown before you can re-enter the PVP instance.
a. You must be free from PVP combat for at least 5 minutes before you can enter a major city.
b. Groups or raids of more than two players will be not be allowed to zone to the PVP instance.
4) Questing in the PVP instance will mirror questing in your faction's instance.
a. You may form groups with players who are zoned into the PVP instance.
b. Dungeons and zones will mirror faction instances.
5) If you are a higher level than a zone you will not be able to enter the pvp instance of that zone.
a. That should eliminate higher level people going around and ganking lowbies.
These are some ideas that I believe Zenimax could use provide the community with the opportunity to have the best of both worlds.
Both options of questing and exploration in a PVP free world, or with the added anticipation and thrill of world PVP.
If anyone would like to add to or help revise any of these ideas your input would be greatly appreciated.