I would like to see the AI attack the highest value targets before considering the easiest targets it can defeat. I have noticed that the AI seems to go after the easiest target, such as a garrison instead of targets that are the real threat. So I would just keep rebuilding cheap garrison units and watch the AI pound them rather than go after my tank which was going to cream them the next turn. The AI, especially the AI's aircraft should go after Leaders, Air Units, Tanks and Ships, even if it cannot do as much damage as it could do against a lesser target.
Perhaps this could be changed for the current SC2 games too...