This is just a suggestion without much though…
Wouldn’t it be better to lock factions for the duration of the faction league and factions be split according to their performance (diamond, gold, silver, etc) and they compete against each other? Obviously rewards need to get better the higher the zone. Maybe allow people to transfer within their zone?
This way the ‘whale’ factions will fight each other and have the competition they want. Rewards for them will be better than lower zones. Also the more f2p people will be fighting each other.