i wish there would be some more diplomacy.
like "how much should i pay you so you'd stop protecting those fools, cuz i really like you and don't wanna kill you yet" (literaly happened to me in my last game. unfortunately i had to declare war on my only galaxy friend and cleanse all his planets(and purge his capital). that even made my fungoid race a bit sad (for a day or two)
or "can i pay you to pretend to be my friend?"
or "let me buy few planets from you"
and so on...
or at least the same thing AI can say to you "hey your outpost\colony is too near. can you please go away?"
Exactly this!
This happens to me pretty much every game where someone I like and dont want to off ends up protecting someone that I hate. When its not in a federation I can at least usually find some way to drag only one into a war and not the other through other alliances they have made (ie, attacking someone i dont care about in order to actually attack someone entirely different) - when it is a federation.. well..
That also brings up the AI's issue of joining 'Loser Leages' - ie, federations that have been continually on the losing ends of wars and have really weak piddly members that can't stand up to aggressors (or even one of my one-system vassals), but haven't been completely eaten up yet due to the wargoals system. Joining up with them when their combined fleet power is less than your vassals' is stupid, yet the AI will do this if someone has been causing enough threat... (The threat system in and of itself also doesn't make that much sense either...) - It doesn't take into account existing friendliness, trust, etc. Also threat shouldn't be generated for defensive wars (unless you're cleansing planets).
If a federation isn't able to protect its members, they should lose faith in their federation after each defeat (and people shouldnt want to join it because the participants would have some sort of 'weak ally' modifier towards any other AI players. Eventually faith in that federation will be so low that it falls apart, and the members will likely have to become vassals if they want protection because nobody sees them as worthy equals. (Or you could maybe calculate weakness based on existing fleet + gross economy, but that doesnt provide an easy way to calculate loss of faith in a federation, unless you check against all the unfriendly/hostile/domineering/belligerent/angry empires (towards any member) powers as well)
...
Also an option to say 'Thats a pretty empire you have there, it would be a shame if something were to happen to it... how about we reach an amiable agreement instead?'
Being able to do a show of force would also be nice. The AI should take a good long look at a fleet thats (literally) over 100x bigger than its own and decide if it reaaaaaallly wants to risk angering said neighbor.
Me w/ 300k fleet parked in their sensor range, 1/3rd of the galaxy in my direct control, and 2/3rds in my combined federation + vassals (which include my pet 'liberated FEs', one of which is ranked 3rd in the galaxy due to a decent 20k fleet & tech), highest kill counts vs. both the unbidden and the prethoryn (I consoled in one when the other started for extra challenge), and the one to defeat both, killer of every guardian in the galaxy except the infinity sphere which didnt get killed, and a strong enough economy to continuously churn out enough ships in a month to defeat most other empires in the galaxy - even while my fleet is deployed: 'Hey, I demand you be my vassal'
Empire w/ 2.5k fleet, 3 planets, no allies, severe and chronic civil unrest after multiple defeats & humiliations & other issues w/ a neighbor I just ate up via liberate & vassalize, and a barely functioning economy: 'Nah'
... refused subjugation modifier should also scale based on strength too...
Sure, my next step is to simply 'liberate and vassalize', for they are but a bump in the road, but thats still painfully unrealistic behavior.
Fallen empires being condescending when I could completely steamroll them in a war also gets at me.. There should be points where they begin to.. at least respect your relative power, even if they dont actually respect you due to ethos. But since they dont respect me, I steamroll them, take their 100% habitability goodies, and liberate the remains into my pet vassals for research agreements. And they still do it after I've done the same to their peers (including any who tried to awaken but got steamrolled in the process anyways).