If the AI doesn't surrender unless at war but the player cannot offer a peace treaty pretty much at will
No. If you are at war you can't talk to them for 16 turns minimum (that was changed I think in Beta 1.6 of DA)... but they can and often do surrender the very next turn to someone else. While surrendering to my empire is... irksome and makes the game go too quickly, typically several weaker AIs will suddenly turn into one large AI in a flurry of activity as everyone surrenders to whom they think can keep them the most safe. You can't go back to peace with a race save the UP event in less than 16 turns with anyone in DA (and TA). This is one reason the Drath super ability can be so powerful used between AIs.
What I'm trying to figure out is whether this is something that should be specified randomly on a per round basis or if there is a reason to leave it on all the time or off all the time. I think it should be one of these three options. The one option I'm not comfortable with is to allow the player to pick and choose it.
The player should not be able to choose. As I said originally, it has a real effect on my playstyle... if surrenders are on I go to great lengths to keep my military rating near zero and go for a blitz win... it'll happen anyway. With it off I build huge militaries and take my time and score grind. The problem is, with the trade fatigue and increased chance of surrendering it has to be a part of your strategy.
This is just one of the differences that isn't going to be easily leveled between the two versions (like mega events, super abilities, allowing custom races). Personally I favor randomly setting it by round, but if you find that distasteful surrenders should always be enabled, because that is the harder variation.
If the AI can decide to surrender even if not at war then I would think surrenders should never be allowed.
Only when at war, but any war will do. A typical, weird outcome will be like this: Turn 1: Thalans declare war on the Snathi. Turn 2: Thalans say, "the snathi are just too powerful" and surrender to the Korx. Turn 3: The Korx were already at war with the Altarians and Torians, now that the Korx are larger, the Altarians immediately surrender to the Korx. Turn 5: The Torians also think the Korx look big, and surrender to them. The above happened to me three games ago while I was playing the Iconians. Less than two months had passed, and the Korx more than doubled in size. During this time period my trade fatigue was up with everyone, so I couldn't even open the diplomacy screen. I lost to the Korx. Hence why leaving it on is harder. Harder isn't necessarily a bad thing.
If the player can be suddenly confronted by bulk surrender without any recourse then I would favor leaving it always disabled.
This is the situation I try to avoid by turning it off, and is always a worry. It will either end your game very early as everyone caves to you, or as is more likely in my game, suddenly everyone but me joins one other empire and I'm crushed under numbers. It makes score grinding very difficult. However, it isn't predictable either. Sometimes the cards will fall just right and no one will surrender. Sometimes the AIs all surrender in a fashion that seems to make sense. But in DA you are really rolling the dice, as once the surrenders start they usually snowball... because whoever gets the first surrender (and their ships and planets) suddenly looks big so everyone just caves to them. The player has no control in this situation.
In DA the waiting period can keep you from making peace with them, since you can't talk to them. I haven't played enough DA though to know if they will surrender to another before the waiting period is over.
They will.
I agree you should have one way of dealing with this option. Always dis-allowing surrenders just makes score grinding a breeze because you give the AI one planet in the corner and pray and pray that they don't influence flip to you while you grind (and building the MCC doesn't help this... its very sad - although many people seem to believe having this building stops flipping). With surrenders ON the game
most of the time will be over quickly, once you have about 60% of the planets the next war declared will be your last, and you can't control when the game ends. This just means that because you don't know if you can score grind for 2 years or 5, its better to blitz and avoid the situation.
Hope that is a little more clear. I'm always happy to help.
~ Wyndstar
Edit: By the way, in my above game, the Snathi had NO military when the Thalans decided to surrender because of that war. I think the way the AI checks in DA is if it is at war it compares itself to every civ to see if it is on the low end and needs to surrender. That is just a guess.