Tower guilds wouldn't have much of an advantage over each since every tower guild would have the ability to recruit many members. It's just a matter of who has more people online at one time.
KOTH is not just about quantity. I know from experience that you can defend castle with few skilled players against many unskilled players, but only to a certain extent. thats when it becomes a matter of quantity. So it's about how many GOOD players you have compared to the other guild(s) really.
This idea is good for family guilds such as Ch4rM because we like having new members, yet we don't want to kick old, unactive members to recruit the new person.