An example could be that every so often the AI would build a structure like an Antagonized Dyson Sphere that spawns an endless flood of ships that attack you. You would have a warning "The AI is building a Dire Guardian Launcher on Murdoch; construction at 55%", and you could either ignore it or go destroy the structure and the fleet guarding it. A bit like Warp Relays, maybe, though it would be good to be able to destroy the partially constructed building. I really like the notion of dynamically generated, mid game mini quests or objectives.
