What I want to be fighting in a game:
- the AIs fleets and armies
- that first early war that's actually interesting/dangerous
- my unwillingness to micromanage 50+ planets and resulting wish to vassalize/federate
- "Invite to Federation: Acceptance: -11"
- "They must be at peace" (to demand vassalization)
- "Warscore: Demanding surrender: -100. Vassalize Wargoal: -100. Won every single battle with 0 losses and occupied all inhabitable planets: +75. Would you like a status quo that magically frees the capital?"
- "You must wait until (...) to declare war"
- Boredom
- Further increase AI bonuses. Everything being decided in the first war is a bad mechanic, but with scaling difficulty, even grand admiral becomes far too easy later.
- Increase the influence of opinion and relative power in the AIs willingness to join a federation. Having every possible agreement with an inferior AI for 40 years, finishing diplomacy traditions, and then giving them twice the ressources they could ever want gives a modifier of... +29. (+15 for trust, +10 for the ressources, +4 for relative power). Being a decadent hierarchy alone gives -30. If the player is in a position where they can heavily invest in diplomacy, that should be a viable peaceful alternative to conquering. This would IMO be far better than the mostly luck-based mechanic we have now, i.e. better hope your neighbours have the right ethics.
- Occupying inhabitable planets, especially the capital, should count more for the warscore, ticking and otherwise. Occupying the capital for more than a year, or more than 2/3 of all inhabitable planets, should be sufficient for vassalization. In my last game I occupied literally every single system and the AI still did not surrender, it's currently quite ridiculous. At the very least "status quo" for vassalization should not magically return the capital -- and please let me vassalize a player at war.