For those players insistent there is nothing wrong with the 4 player setup of the game:
In addition to winning the game with 7 castle/strongholds:
"A player must posess 10 power tokens to support those new acquisitions with the necessary infrastructure to claim victory"
This means if you do not have 10 power tokens, you do not win the game at that time.
If at anytime you acquire 10 power AND have 7 strongholds/castles that player immediately wins.