I think capture flag should be removed from the game.
I think this system would make much more sense and much less exploitable if exploitable at all:
If one nation make an attack from La Habana to Mariel for example the defenders would have 30 mins in order to prepare the defense, every player who wants to participate in the battle should check in in the port where the attack starts and move to the battle from there. When the 30 mins ends the port battle would open and only the players who checked in would have access. There would be no limit to the number of players who can check in.
That would force every player who wants to participate into the battle port to start the attack from the port where the attack was launched.
There would be unlimited attacks, so if one player buy the attack from one port that is far away from the port target in order to frustrate/trolling the attack another player could buy another attack from a closer port.
Every player would need to check in in any port where the attack was bought and start the attack from there.
That would avoid players logging off near the attacked city, players from the same faction putting the flag in combat on purpose, people purchasing flags in order to frustrate an attack etc, etc
The further away the attack is launched the more time the defenders would have to prepare the defense, you couln't make an attack that is more than 1 hour traveling.
I think the flag system is really exploitable, not good and not realistic at all, every attacker should move from the port where the attack is originated to the attacked port as in real life.