I would like to suggest a possible solution to the whole Migration problem with not only Chinese servers but possibly all servers.
Why don't you make the migration based on Overall power of a given kingdom... Total the power of all players(or even only the active players for the past 7 days or so) and base top kingdom on the one with the most power... This won't eliminate a few top players migrating but It would definitely prevent entire kingdoms from switching sides while still allowing players to move from one kingdom to another... It will be a lot harder to abuse this system than the current one based solely on the amount of cities a given kingdom has. Another Idea would be to total the castle levels of all active players in the kingdom and rate kingdoms on that... Or we can go even further and take that total number of castle levels and divide it by the number of players to get the average castle level for the kingdom, BOOM problem solved based on development of average castle level! And to solve issues such as creating alternate accounts to lower average castle level, only take into account players over certain points/castle level which would increase based on the power of average player overtime.
Let me know If anyone has any thoughts, improvements, or ideas to add to mine.