I support 100% the idea of making the historical scenarios as historical as possible. It's not everyone who wants to play what-if scenarios. I only play against the AI and I really like to play scenarios where the moves reflect the actual moves, because I'm interested in the history, above all. I think many players of this type of game, against an AI, are like that. So don't change that approach! The answer is to provide what-if scenarios as alternatives, as people have suggested. I wouldn't touch the alternatives, but others would, clearly. Also, I think if I wanted a non-historical fight I would go PBEM.
So far, playing this, I'm like others have described themselves above - useless - and hence I've not been noticing many crap AI moves. Seems good to me so far.
"Historical" can mean different things to different people. For me, slavishly following historical events is in fact ahistorical. General X did action Y because General A did action B in history. But if you are playing General A and do action C instead, it may well be illogical for General X to do action Y in that circumstance - you are allowing the player to deviate from history, but force the AI to follow it even if it makes no sense? To me this isn't history.
To me, the historical part of historical gaming is giving both players the same resources, spatial dispositions, and other characteristics and restrictions that their historical counterparts had to allow players both to emulate and deviate from the actions of these counterparts. History is not necessarily the way it is, it is only contingency so, therefore forcing the player or AI down tramlines feels wrong to me.
Still, to each their own - that's the other great part of this hobby. Making variations that suit all tastes does not have a huge development overhead in a flexibly designed game.