That's true -- I think the match format would have to be set up in a way similar to Conquest in Battlefield where teams get points for holding objectives. In that case, if the opposing team has more objectives, the AI can't just play defensively because then your team would simply lose -- so the focus on the AI needs to be on score rather than maximizing each player's performance.

Alternatively I think if it were configured in such a way where one team was explicitly attacking and the other explicitly defending it might work out ok as I had envisioned it... though I think that would come with its own problems.