I guess the suggestion would be an improved campaign AI that messes with the fleets allowing for coordinated attacks/defences, one that is more aggressive and responds to both the player's actions and the other AI factions' as well. They should be sending to your location the best fleets they have and try to retake the lost colony (or even destroy your own) while that colony is still undefended as the player had little time to gather up a defence fleet to defend the new colony. You have a new colony and a new source of income, but by doing so you are also crippling the enemy faction and they don't do much to stop you.

You know that when you are trying to take an enemy colony the enemy defence fleets will engage you but after that. The same does not really happen in Starsector, your actions only make you stronger and there's no risk other than what you are during that exact moment. The issue is at some point (and often quite quickly) the enemy marshall with gather the armies of all vassals and try to retake the castle, and when they do, their combined armies will often be upwards of 1.5k men. The castle was being guarded by 200 men and you managed to beat them with an army of 300, not bad. You take an enemy castle, and gather up some men for a garrison. Let's take Mount and Blade as an example. It shouldn't be possible for a single player to destroy one of the main factions of the game without having to slowly wear down the supply lines and mess with the chain of command of a faction, just as a faction 10 times the size of the player shouldn't just sit around and do nothing as they see their fleets slowly be destroyed. The AI feels too passive to threats and as such some features like the 'taking down an enemy admiral to reduce the number of fleets the enemy can command' have no impact and only further contribute to the player snowballing the game as the game progresses. If the player starts attacking the trading fleets of some faction (or even their main combat fleets) I expect the enemy to send out scouting fleets actively looking for the player and call in for reinforcements to engage and strike back, or at least gather a fleet of hundreds of ships and raid the player's bases. If the player starts attacking a massive faction such as the Hegemony or Tri-Tach and has a colony somewhere, the enemy should gather up a 'screw you' fleet lead by an admiral and remove that colony from the map, or take it for themselves, instead of staying passive and engaging the player only if they stumble on it or when defending their own colonies. One of the ideas was to make the AI factions more aggressive towards the player.

Killing an enemy admiral and stopping his/her fleet from spawning back further contributes to the snowball effect the game suffers in the late game right now. After a discussion in the discord server regarding 'kill target' missions in RPGs and how something similar could be implemented in Starsector we got to a conclusion:

Mount and blade campaign ai