CA could make an immediate, major improvement to the BAI just by eliminating the ability for the AI and the player to garrison buildings. In a more realistic game, both the AI and the player could choose to garrison any building or structure on the battlefield, which would keep the army together. Instead, (and probably due to 3D graphics limitations), only a few scattered buildings can be garrisoned, and they're never close together. The player is smart enough to choose one building to put troops in, with supporting troops nearby, using surrounding buildings to protect the flanks. The AI never does that. It just occupied all possible buildings with single units, while the rest of the army remains somewhere off in the distance. This allows the human player to pick off units one by one. Even when driven out of a building by artillery fire, the AI unit never rejoins the rest of the army, and the rest of the army never provides support. They're sitting ducks.

I know there's a lot more that could be improved in the BAI, and this doesn't happen all the time because not all battles included buildings that can be occupied. But this is such a failure of a game "feature" that they should really just remove it. Sometimes simplifying the design is the right answer to improving it, instead of piling on more features that just become player exploits. I doubt that CA would ever do this, but it would immediately improve at least some of the battles.