The lesson to be learned from Blackwater Blade is that players enjoy a big battle that is pretty fair all around. As is stands right now BWB is the best campaign to play in for some great PVP but it doesn't have to be that way. Once some of these characters hit VR 1 the only option they have is to enter another campaign with all levels and most likely get owned by VR 14's, which can be deflating.
So my recommendation to ZOS is to add more campaigns but make them special campaigns. I can't take full credit for this idea, me and a friend.guildie of mine were just chatting about this and our ideas meshed. They should add 2 or 3 more campaigns. One would be a VR 1-5 campaign, another would be VR 6-10. I don't feel another for VR 11-14 would be necessary, usually by VR 10 you are pretty survivable in most fights.
This would ease people into PVP and also not get them to get so frustrated they play something else, because no one likes being owned over and over just because you're "under leveled". Not everyone enjoys the vet zones and might feel that they are forced to level in PvE in order to PvP and be effective. Adding these campaigns would alleviate a lot of frustration by lower VR's and even make them grow with some other players just like the rest of us did at the original launch.