If Grey Host is going to be the only normal Cyrodiil campaign going forward, then we either need to get rid of faction lock or introduce a Mercenary faction where we can join whichever the lowest population faction at the time is.
I have 15 characters with a pretty even split across the alliances. If my only options going forward are to play Vengeance or buy a faction change token to play on a character I'm not faction locked to, I'm just going to stop playing Cyrodiil entirely.
I do not like Vengeance in the slightest. I know I'm not alone in this. I also know that plenty of my guildies and friends have toons on multiple factions as well. Something needs to be done or you are essentially barring a large portion of your playerbase from being able to play Cyrodiil with their friends.
Let us choose to be a Mercenary: if we toggle Mercenary on for that character, anytime you queue for Cyrodiil on that character, you join the faction with the lowest current population. If a workaround like this can't be implemented, then Faction Lock needs to be done away with.