The solution has been proposed, yet you seem unwilling to implement it. A simple timer will make all the difference.
How is exploiting a flaw in the game design NOT considered an exploit? It IS, by definition. The attackers who use this exploit, which will be everyone at every port battle until you decide it's actually worth fixing, are given free entry to the battle. No point in screening at all. They can circumvent a huge proportion of the defender's defenses, thus increasing their chances of taking the port. Pre-logging favours the attacker. It's an exploit.
Remember when a single basic cutter could drag the entire assault fleet into battle? Every nation did it and many ports were lost because of that exploit. This is just as serious and needs to be deal with swiftly.
We're not asking for miracles, we're asking for a timer. It doesn't get much simpler than that.
If you continue to deny the severity of this issue, and people start losing ports as a direct result of this exploit, they will start leaving. I find it hard to believe that you can't just announce emergency maintenance and add a timer that stops people benefiting from this exploit. With all the great things you've accomplished in the development of this game, a simple timer is a minor task at best.