No game is perfect for everyone but I was thinking that there could be a way to expand PvP a bit to the PvE areas. Here are my thoughts.
1. There would be a duplicate world that is open PvP everwhere so PvP folks can do their leveling and all the overland quests and such in a PvP enabled world. Same servers, different zones maybe. Kind of like what they do when there are too many folks in a zone the servers just spin up a new instance.
2. All housing, battlegrounds, dungeons and trials would remain the same. No need to change there. So from PvP and PvE everyone would enter the same queues. Basically you walk up to the sewers or whatever dungeon door in either world and you go to the same ones with folks from both PvE and PvP worlds. When you exit the area, you go back to where you came from or maybe based on some sort of PvP enabled flag.
3. Folks could choose to play in either PvE or PvP ESO at anytime. Wether your friends are in the PvE or PvP world, you could see them online. Say you join a group with them, then you can port to the leaders world and start doing quests or what have you together. If you want to Raz save the Queen while being chased around by other players then you can, but if you tire of it then you unflag PvP and return to the PvE instance. I would also go as far as to say that the only safe place is death, a respawn point or your house. Make it interesting.
4. There could also be a new PvE Cyro available. Maybe its slightly changed, like a post war Cyro that is rebuilding or something and then they can add more PvE quests to it. More game expansion possibilities. However, in the PvE Cryo, you can't gain AP or anything related to PvP Cyro. This could be the same for Imperial City as well, but I don't have much experience with that zone.
Basically there really is no need to change quests or anything like that. Just duplicate some instances and work out a few game mechanics to allow for things to work right. Maybe there are hubs in town that you can click on to change instances or maybe a checkbox on your character.