What's with the AI? No matter the difficulty, you can just easily cheese them by sending some bombers to nuke their capital. They fight well but even as their capital gets gonked by an enemy fleet, they might have a 50 million fleet supply sitting next door and having a Vasari-themed slumber party. In a multiplayer fight, I even saw the AI make some ships and they ignored the fleet blasting their families back at home.
AI should spend more time worrying about their capital since the main game mode is capital victory (or colonization but that's not important here). Even if they built a million turrets, they don't bother turning them making them all useless.