I think Shambles was just offering suggestions of how to raise the morale of the AI troops so they don't run away--all of his suggestions do that (harder difficulty setting, increased honor, not outnumbering your opponent too much, etc.). Turning off morale will solve this problem in one parameter change.

As far as non-morale-related repositioning by the AI goes, I think the only thing you can do is manuever your troops in such a way that they don't have anywhere practical to go. The AI is somewhat programmed to behave in Sun Tzu fashion, so if you are familiar with those basics, predicting what they will do given a move by your troops becomes pretty easy.

If you try the scenario you mentioned with 4 hcavs instead of 1 against 4 muskets, set them to Honor 3-4 (assuming your muskies are honor 2-3), and keep them together, my guess is you should be able to charge the muskets (not head on, but from an angle) and route them rather easily. If you want to control the muskies, well, I'm not aware of any way you can force the hcavs to stay together and charge you. Maybe some of the stat/AI wizs here will see your post and comment.