A little while back I saw some posts on the steam forums about how the game's diplomacy system in its current state can be a bit exploitable for the player. I've been sitting on an idea about how the existing system could be modified slightly to make it harder to buy up all the AI empires as allies for a council victory.
Now I've heard that sven and arioch are planning to revisit this part of the game in the near future - and I don't want to intrude on anything they might have planned - but I could probably make it into a mod if as a kind of holdover in the meantime if anyone is interested. Though this sort of thing is a lot more subjective than changing how the AI uses it's resources.
The basic idea is that when showing the menu of possible agreements to the player, in addition to checking their relationship with the player, the game also checks the relationship with any allies the player might have.
If they're at war with or simply dislike any of your allies, then an alliance is out of the question. Alternatively, if they dislike any of your allies then getting an alliance could just be prohibitively expensive instead. I think an important detail would be to make sure to indicate which ally is the point of contention in the menu, so that the situation is always clear to the player.
Also, I think in order for this to be fully fleshed out I'd have to handle AIs breaking alliances with the player in the case that one ally wants to declare war on another.
The end result is that the player is restricted to buying alliances with only groups of AIs that mutually like each other.
Another idea I had, that would probably require creating a bit more npc dialogue text, would be to make it that if the player buys an alliance with an AI that has more votes, that AI now expects the player to vote for them. If the player doesn't, they break the alliance after the council meeting. So for the player, buying an alliance with a stronger empire is not about buying votes, but giving up votes for guaranteed good relations with a potentially dangerous neighbor.
It could also be a fun situation if the player has multiple allies that are expecting votes from them - and the player has to choose.
Thoughts?