Okay, it seems that such a feature is not very common, and it goes by the non-standard name of "resume a game from a replay." StarCraft II has this feature, which allows you to replay past games for practice. Unfortunately, StarCraft II cannot be played permanently offline, so it's not to my liking.
In Zero-K, I've decided to do this: I manually save the game multiple times during a match, so after the game ends, I can reload these saves and replay the game from different points in time.
One drawback I've noticed is that for the first few seconds after loading a game, the AI seems to be in a chaotic state and will definitely retreat, even if I'm easily defeated. After about 10 to 20 seconds, the AI appears to have figured out the situation and starts to re-engage. I hope this doesn't significantly affect the AI's performance level.
Thank you all for your answers. I enjoy the intelligent unit AI in this game, which makes them feel like trained soldiers, and that's one of the reasons I came here. I hope we can keep enjoying this game, and I wish everyone happy gaming.
