More on the save system:
"Itís not cheating (at least, it was never made clear to me that it was cheating) to simply reload if you donít like how something went down. In fact, plenty of single-player games of the past 15 years were balanced with save-scumming in mind, so if you did choose to take the high road, you were often presented with an imbalanced (unfair) level of challenge.
The whole idea that ďno, you donít even have the ability to go back after youíve made a decisionĒ really changes the way that a decision plays out. Suddenly, the idea of true uncertainty entered into single-player gaming. What will happen after I make this move? I canít just save it, find out, and then load my game. I have to make a kind of educated guess. The optimal move is ambiguous, and I express my skill at this game by trying to decide between multiple seemingly equal options. You can only feel this if you donít have the power to look into the future, which save-scumming gives you."
~ Keith Burgun, http://keithburgun.net/the-journey-to-game-design-theory/
If a save system is included, which I still don't think is a net positive, even though it has benefits, I think it is important to balance the game as if the system didn't exist. The AI can't reload, so their difficulty level shouldn't be affected by save-scumming. This is assuming that the AI are going to be roughly/exactly symmetrical with the player in terms of how they play, their goals, and how they interact with the player as opposed to other AI.
Which I think they should, otherwise it wouldn't feel like you are competing with them. The player shouldn't feel special/priveleged/different from the other barbarian tribes at the start - they should have to earn their special place. It shouldn't be because of high level asymmetric goals and gameplay mechanics. (There are some exceptions, such as mocking up AI to AI interactions that approximate player to AI interactions, without going through all of the thematic add-ons that are done for player experience. But the gameplay result must be very similar to the player one for the player to see the AI as interesting opponents that are on the same level.)