Can you force PvP balance?

All races aren't created equal in a MMORPG. As much as developers try, players never distribute themselves evenly among a game's available races. In PvE that doesn't cause much of a problem, who cares if there are more humans than gnomes in World of Warcraft? But in PvP real problems of balance appear. In World of Warcraft the problems are apparent: On most servers Alliance outnumbers Horde up to 2:1, while on some few servers players conspired to boost Horde numbers and there Horder outnumbers Alliance. Numbers are important for overland PvP. If one side brings 200 people to a fight and the other side only 100, the final result of the battle is foreseeable. But if you restrict the numbers, like WoW does with battlegrounds, suddenly the more numerous side is at a disadvantage, because they are stuck much longer in waiting queues.

Now PvP is not the central feature of World of Warcraft, and imbalances like this don't matter very much there. But a number of upcoming games are more PvP-centric, and have realm vs. realm wars, in which one side can conquer the territory of the other side. Examples would be Warhammer Online : Age of Reckoning (WAR) or Pirates of the Burning Sea (PotBS). What if in WAR the chaos side outnumbers the empire significantly, or the other way round?

If video games have one bad influence on players, it is that they teach us the wrong belief that you can always win. This is because the computer opponents are designed to lose most of the time. Players got so used to winning all the time, that they go to great lengths, including cheating, to not lose. Unfortunately in PvP by definition some player must lose, not a computer who doesn't mind. That causes a problem with realm vs. realm type of PvP games, because even a small initial imbalance can cause people to think that one side is "better" than the other, and that causes players to choose the apparently "better" side preferentially, thereby increasing the imbalance. Dark Age of Camelot hasn't gotten its realms balanced after 6 years of existence. Although both WAR and PotBS say the plan to have "resets", after one side wins, it is unlikely that in the next round on the same server a different side suddenly dominates. If somebody has a high-level empire character in WAR and the empire just crushed the chaos side, he isn't going to reroll a chaos character for better balance. But maybe the chaos guy who got crushed will give up and move over to the winning side. And as long as one side significantly outnumbers the other, the more numerous side will win every war, even if they lose a few battles.

So I was wondering if a numerical imbalance of one side over the other could somehow be prevented. To take World of Warcraft as an example, WoW already has waiting queues for full servers encouraging you to play on a less populated server instead. What if those login queues worked separately for Horde and Alliance? Instead of capping a server population at lets say 4,000 players total, it would be capped at 2,000 Horde and 2,000 Alliance players on PvP servers (where you can't have characters on both sides). I don't think WoW really needs that change, or Blizzard would do it now, but for a new game like WAR this would be possible. Do you think the number of players per side on a Warhammer Online server should be capped, to avoid one side outnumbering the other side by a too large margin?