Cuddles' Law: The volume of a player's whine is directly proportional to his/her VIP level.
Although there would obviously be a problem on newer servers, why not just institute a minimum level - say sixty - for players to actually participate in guild warfare? While some people will take their alts relatively high, many will not. A guild full of 50s with one or two 60s could block, or run interference, but not pose any sort of actual threat. It's not a perfect solution but it could be a step in the right direction.