I wish they make it an option so I could at least choose no surrender. I have seen them surrender too often, and if you kill the homeworld, they will be very likely to surrender. I just quit a game because of it. It was with 3 systems, red owns a system all by itself, plus its homeworld and 5 planets in the contested system. I killed homewold and instead of relocating to a new world, with a full system out there that they own all by themselves, they surrendered.
Seriously if the disable surrender is ever available, I would never play a game without it. It makes all the early on bullying(on the player, especially in unfair and up) so much more satisfying as I get that sweet revenge, surrender robs you of that satisfaction, that and of couse the battle of the line is always fun. So if any devs are reading, please give us a disable surrender feature, at least please give me since I play exclusively against AI:)