In many ways, the game you use for an AAR is actually pretty irrelevant, the most important things are how much you enjoy the game and the roleplaying you bring to it. You can ignore certain game features in your AAR and add anything you like that doesn't actually occur in the game, or expand on the reasons and background to incidents in the game. Fluff doesn't necessarily have to come from the game, whether additional characters, using pictures from outside the game or whatever you feel can bring your story to the screen.

Good luck with the AAR, I'll certainly read it, MTW is still my favourite Total War game.