As one if the poster's above mentioned the only way to make it more fair considering the faction balance is to make it guild based, and completely ignore the faction stuff.
If the guilds actually have something to fight for that will benefit the guild later on its the best you can get from open world pvp.
Raw open world is great but its never going to happen in a game that has ANY factions even if you somehow encourage ppl to make chars on both sides ( the 8 buffs you so fear for example) there will always be imbalance or ppl will simply switch to the char on the other side when they see it winning.
As for the other 2 options pvpve balanced and capped population they belong in instances for example warzones. If you can make bigger warzones say 24 v 24 or even 100 v 100 its still going to be a warzone and you should not call it open world especially if there are objectives that give advantages/points
So considering your poll has only 3 options ( raw, guild based and bigger warzones - which is not open world pvp) and the fact that you cant fix faction balance in a open uncapped world no matter how hard you try - there is no real choice there
I'm sure all would welcome bigger warzones specially if they are event based once a week/day with some cool story/rewards.
But if you want to do somehting for the open world pvp it has to be guild based with rewads for the winning guild.