Keep in mind that joining a faction next season will cost more money if the faction is already stacked and that with the way the ZC payouts work, active pvp players will earn more money in a smaller faction.
Once faction is old and mature, money will be not restrictive enough. Ofcourse i am considering new players being related to existing faction members, not just random players. So they can get money as welcome present from inside of huge faction.
Also I could spam enemy faction with several alts at the beginning of the season, just to prevent new members joining them?
What is the rational relation between count of all faction members and let's say "average player count in action"?
Are/will be players free to jump from one faction to another according to mechanism you have described in here?