Not sure if this is a better question for General or PvP, since PvP seems to be mostly about class balance/arena/rbg.
Players on PvE realms who want to PvP can flag themselves for PvP, right? So why can't we just have every realm be like that? Then the people who want world PvP can flag themselves and those who don't can do whatever they do. This seems like a simpler solution than: being unhappy with your realm; paying $25 for an xfer; xferring away from friends/good realm. Maybe extend the flag to 30 minutes or an hour or have a "continuous flag" option.
Realms would really be no different than they are now, except that instead of people complaining about being ganked, people might complain that there aren't enough victims to gank.