I prefer to lurk rather than contribute, but on the topic of migration I feel it's pretty clear that some things need to be said. Migration makes the game much less fun. It encourages kingdoms *not* to expand, and then the late game can just be ruined by a large number of players agreeing to switch to another kingdom.
With free and unlimited migration, people could also sabotage their kingdoms too. You can start an account, and run the biggest house, with the intent purpose to purge all players and give up all the houses. You could kick 135 players, and expose 3 cities, and then switch kingdoms, crippling the original kingdom.
I still enjoy playing this game, but I feel this negatively impacts the pacing of the game because it's so exploitable. There's lots more about migration that doesn't work well, but I don't want to write an essay. I'm sure others have complained about this, but I feel this topic is the most important of all the game design in Art of Conquest.